diff --git a/src/daily-cache.ts b/src/daily-cache.ts
index af76640..c5439c3 100644
--- a/src/daily-cache.ts
+++ b/src/daily-cache.ts
@@ -623,10 +623,14 @@ export function withDailyCacheLock<T>(fn: () => Promise<T>): Promise<T> {
 
 export const MS_PER_DAY = 24 * 60 * 60 * 1000
 export const BACKFILL_DAYS = 365
-// Keep 2 years of history so the longest bounded UI period (6 months
-// via `all`) and the uncapped `lifetime` period both have headroom to
-// read from cache while old entries get pruned.
-export const DAILY_CACHE_RETENTION_DAYS = 730
+// Ten years. This cache is the ONLY durable record of carried days (their
+// session files are long deleted), and the uncapped `lifetime` period reads
+// from it via buildDurablePeriod, so pruning at the old 2-year mark would
+// have replayed the lost-history bug in slow motion at that horizon.
+// Measured envelope keeps this honest: ~2.3 MB / ~11 ms JSON parse per 730
+// days of fully dense data, so even a decade of daily use stays ~11 MB and
+// well under 100 ms on the polling path.
+export const DAILY_CACHE_RETENTION_DAYS = 3650
 
 export function toDateString(date: Date): string {
   return `${date.getFullYear()}-${String(date.getMonth() + 1).padStart(2, '0')}-${String(date.getDate()).padStart(2, '0')}`
diff --git a/src/quota.ts b/src/quota.ts
index 48d47ed..17b99d5 100644
--- a/src/quota.ts
+++ b/src/quota.ts
@@ -76,6 +76,10 @@ export function computePace(window: QuotaWindow, now: Date = new Date()): QuotaP
   const elapsedSeconds = windowSeconds - remainingSeconds
   const expectedFraction = elapsedSeconds / windowSeconds
   if (expectedFraction < QUOTA_PACE_MIN_ELAPSED_FRACTION) return undefined
+  // A NaN usedFraction (e.g. derived from used/limit with limit 0) would sail
+  // through the clamp below (min/max propagate NaN) and poison every pace
+  // field. Unknown usage means no pace, not a NaN pace.
+  if (!Number.isFinite(window.usedFraction)) return undefined
   const used = Math.min(Math.max(window.usedFraction, 0), 1)
   if (used >= 1) return undefined
 
diff --git a/tests/daily-cache-carry-forward.test.ts b/tests/daily-cache-carry-forward.test.ts
index 1d8f7e9..62197fa 100644
--- a/tests/daily-cache-carry-forward.test.ts
+++ b/tests/daily-cache-carry-forward.test.ts
@@ -388,7 +388,7 @@ describe('never-lose invariant: invalidations with vanished sources', () => {
   })
 
   it('retention still prunes ancient carried days after a rebuild', async () => {
-    await seed({ days: [seededDay(), day('2020-01-01', { claude: slice(1, 1) })], complete: false })
+    await seed({ days: [seededDay(), day('2010-01-01', { claude: slice(1, 1) })], complete: false })
     const out = await ensureCacheHydrated(noSessions, () => [], 'cfg-A')
     expect(out.days.map(d => d.date)).toEqual([daysAgoStr(30)])
   })
@@ -483,7 +483,7 @@ describe('adoption union across older cache files', () => {
     const old = {
       version: 13,
       days: [
-        day('2023-01-01', { claude: slice(1, 1) }),
+        day('2010-01-01', { claude: slice(1, 1) }),
         day(daysAgoStr(15), { claude: slice(5, 2) }),
         day(daysAgoStr(0), { claude: slice(99, 9) }),
       ],
diff --git a/tests/daily-cache.test.ts b/tests/daily-cache.test.ts
index 7cff2ea..6ae0707 100644
--- a/tests/daily-cache.test.ts
+++ b/tests/daily-cache.test.ts
@@ -260,7 +260,7 @@ describe('addNewDays', () => {
   })
 
   it('still prunes when newestDate is valid', () => {
-    const old = '2020-01-01'
+    const old = '2010-01-01'
     const recent = '2026-04-10'
     const base: DailyCache = {
       version: DAILY_CACHE_VERSION,
@@ -269,7 +269,7 @@ describe('addNewDays', () => {
       days: [emptyDay(old, 1), emptyDay(recent, 2)],
     }
     const updated = addNewDays(base, [], recent)
-    // 730-day retention from 2026-04-10 → cutoff ~2024-04-11; 2020-01-01 must be gone.
+    // 3650-day retention from 2026-04-10 puts the cutoff in 2016; 2010-01-01 must be gone.
     expect(updated.days.find(d => d.date === old)).toBeUndefined()
     expect(updated.days.find(d => d.date === recent)).toBeDefined()
   })
diff --git a/tests/providers/vercel-gateway.test.ts b/tests/providers/vercel-gateway.test.ts
index 2aa7108..4964003 100644
--- a/tests/providers/vercel-gateway.test.ts
+++ b/tests/providers/vercel-gateway.test.ts
@@ -101,7 +101,9 @@ describe('vercel-gateway end-to-end (parseAllSessions network path)', () => {
       ok: true,
       json: async () => ({
         results: [
-          { day: '2026-06-01', model: 'openai/gpt-4o', total_cost: 12.34, input_tokens: 1000, output_tokens: 500, request_count: 3 },
+          // Relative so the rolling 6-month dashboard window always contains
+          // it; a fixed date here starts failing once the window moves past it.
+          { day: new Date(Date.now() - 15 * 24 * 60 * 60 * 1000).toISOString().slice(0, 10), model: 'openai/gpt-4o', total_cost: 12.34, input_tokens: 1000, output_tokens: 500, request_count: 3 },
         ],
       }),
     })) as typeof fetch
diff --git a/tests/quota.test.ts b/tests/quota.test.ts
index bed4638..1be12b1 100644
--- a/tests/quota.test.ts
+++ b/tests/quota.test.ts
@@ -179,3 +179,18 @@ describe('buildPlanQuota', () => {
     expect(quota.windows[0].pace).toBeUndefined()
   })
 })
+
+describe('computePace NaN guard', () => {
+  it('returns undefined for a non-finite usedFraction instead of a NaN pace', () => {
+    const now = new Date('2026-07-15T00:00:00Z')
+    const win = {
+      kind: 'weekly' as const,
+      usedFraction: NaN,
+      resetsAt: new Date('2026-07-18T12:00:00Z'),
+      windowSeconds: 7 * 24 * 3600,
+      source: 'live' as const,
+    }
+    expect(computePace(win, now)).toBeUndefined()
+    expect(computePace({ ...win, usedFraction: Infinity }, now)).toBeUndefined()
+  })
+})