3 months? That's peanuts. Having too many Arch boxes, back in '12/'13 I had one that was 9 months behind, with the big filesystem movearound and sysvinit->systemd change happening in that period. It took a couple of hours of work, but the upgrade went through fine in the end.

I'd suggest you do automated testing of at least 6 month old system upgrades. Because users are going to do it, and much complaining will ensue when it breaks their system.