09-15. I had an A2 and an A4. As an owner of AKs, I may have been spoiled but I found the M16s to be truly awful in terms of the cleaning maintenance. To be fair my sloppy ass A2 was more forgiving than the A4. The A4 was nice and accurate in garrison but downrange I talked my armorer into getting me my A2 back. The dust was too much for the A4 to handle.

I was a Forward Observer but was put in an aviation unit for some reason so I spent a good amount of time RTOing adjacent to various helis. I can say without a doubt that we had helis down for maintenance every day, sometimes for multiple days at a time.

This all circles back around to "the older the better" theme from my previous comment. Chinooks are an ancient platform but they're super reliable and nearly never broke down outside of schedule. The M16A2 I had did have like 1/8" of play in it between upper and lower receiver but I did keep it working. God knows how many rounds went through that thing. But both of those things are what, like 'Nam era? All the truly durable stuff is old school. I'm just saying the new stuff is garbage.