Your agent's memory needs an expiration policy (or it'll drown in its own history)

Your agent starts sharp. Clean memory, focused responses, makes good decisions. Six weeks later, it's citing outdated project requirements from December and referencing team members who left the company.

The problem isn't that your agent forgets things — it's that it remembers everything equally.

Most memory systems are digital hoarding

I watched one of our coding agents slow to a crawl because its memory contained 847 entries about a client project that ended two months ago. Every query was swimming through dead context, looking for patterns in information that no longer mattered.

The solution isn't bigger memory — it's memory that expires intelligently.

Memory without expiration is just accumulated noise.

Here's the expiration policy that works

I built a three-tier decay system that mimics how humans actually forget:

• Hot memory (7 days): Everything gets stored, high retrieval priority
• Warm memory (30 days): Only significant events and decisions survive
• Cold storage (permanent): Core knowledge, established patterns, and explicit "remember this" items

The magic happens in the transitions. When moving from hot to warm, the agent evaluates: "Did this change how I work? Did this establish a new pattern? Was this explicitly marked as important?"

If not, it gets compressed into a summary or deleted entirely.

The implementation is simpler than you think

Add this to your agent's daily maintenance routine:

MEMORY_DECAY_RULES = {
  "hot_to_warm": {
    "age_days": 7,
    "keep_if": ["decision_made", "pattern_established", "explicitly_marked"],
    "compress_rest": True
  },
  "warm_to_cold": {
    "age_days": 30,
    "keep_if": ["core_knowledge", "recurring_pattern", "user_preference"],
    "delete_rest": True
  }
}

Every night, your agent reviews memories by age and applies these rules. Routine status updates get compressed. Temporary project details get deleted. Important decisions and learned patterns get promoted to permanent storage.

What actually survives the decay

After running this system for three months, here's what stays in memory:

• Your working preferences ("always use TypeScript for new projects")
• Established patterns ("when deploying, run tests first")
• Key decisions and their reasoning
• Contact information and relationship context
• Explicit "remember this" instructions

What disappears:

• Daily status reports older than a week
• Temporary project details from completed work
• Routine confirmations and acknowledgments
• Outdated information that's been superseded

The result: faster, more relevant responses

My agents now respond 40% faster to complex queries because they're not sifting through months of dead context. More importantly, they make better decisions because their memory reflects current reality, not historical noise.

Your agent's memory should be like a well-organized filing cabinet, not a storage unit where everything goes to die. Give it permission to forget the unimportant stuff, and watch it get dramatically better at remembering what matters.