I totally get your dilemma - it's like being stuck between a rock and a hard place! You've got this 20-year-old Mitsubishi PLC that's absolutely critical to your operations, but the manufacturer has abandoned it and finding replacement parts feels like searching for unicorns. Both migration and maintenance seem equally scary, right?

Here's what I'd suggest: First, don't panic. Many companies face this exact situation. The key is to approach this systematically. Start by creating a detailed inventory of all your PLC modules - every part number, every connection, every piece of code. This gives you a clear picture of what you're working with.

For the maintenance route, you can partner with reputable suppliers who specialize in legacy systems. They can help you source equivalent parts, set up availability alerts, and even help you monetize idle spares through surplus programs. But here's the catch - you're essentially playing a waiting game where the parts pool keeps shrinking.

For migration, Mitsubishi Electric actually offers upgrade paths for their legacy equipment. The good news is they can often migrate your control programs with minimal engineering effort, which reduces the risk significantly. Modern PLCs also give you better performance, connectivity, and future-proofing.

My advice? Consider a hybrid approach. Start planning your migration now while maintaining your current system. Document everything, test your backup systems, and maybe even run a parallel system during the transition. This way, you're not caught off guard if something fails, but you're also moving toward a more sustainable solution.

What's your biggest concern with either option? Is it downtime, cost, or something else?