Hey there! That's a fantastic question that every maintenance manager should be asking. Let me break this down for you based on what I've learned from industry experts.

First, identifying when a PLC part is about to be discontinued requires proactive monitoring. You should:

1. **Subscribe to manufacturer notifications** - Most automation suppliers like Allen-Bradley, Siemens, and Mitsubishi have product change notification (PCN) and end-of-life (EOL) alert systems. Make sure your purchasing team is on these lists.

2. **Use lifecycle monitoring tools** - Services like SiliconExpert or Octopart can track component lifecycle status across your entire bill of materials.

3. **Build supplier relationships** - Your trusted automation distributors often get early warnings and can give you heads-up before official announcements.

4. **Watch for warning signs** - When lead times start stretching (8-16 weeks is common now), prices increase, or you see 'not recommended for new designs' labels, that's your red flag.

Now for the 5-year buffer stock strategy without breaking the budget:

**Prioritize ruthlessly** - Only stock what's truly critical. Focus on PLCs, VFDs, HMIs, and motion control drives that control your line-critical processes. These are your 'single points of failure.'

**Standardize platforms** - If you can standardize on common PLC families across machines, you can cut spare parts spending by 20-30%. Fewer unique parts means lower inventory costs.

**Use cross-reference support** - Companies like Industrial Automation Co. offer cross-brand compatibility guidance. A Siemens or Mitsubishi I/O module might replace an obsolete Allen-Bradley part at a fraction of the cost.

**Time your purchases strategically** - Buy buffer stock before seasonal production peaks or fiscal shutdowns when budgets are more flexible. Consider 'last-time buys' when you get EOL notifications.

**Explore parts agreements** - Rockwell Automation and others offer agreements where you get access to parts without owning them outright. This reduces obsolescence risk and ties costs to actual usage.

**Build a local stock strategy** - Instead of depending solely on OEM channels, work with local distributors who can provide verified inventory and faster response times.

The key is balancing inventory cost with the risk of unavailability. Start with your most critical components, build relationships with multiple suppliers, and use data-driven decisions rather than gut feelings. This approach keeps your operations running while protecting that maintenance budget!