"Sometimes houses just aren't perfectly square, ya know?"
Yeah, that's the truth. Ever tried replacing windows in an older home? I swear, nothing lines up right. One thing I've learned is to always have some extra shims handy—saved me more than once. Also, don't underestimate how much caulk you'll need. Seems like no matter how careful you measure, there's always a gap or two that needs filling...
Gotta disagree slightly on the caulk thing—if you're relying heavily on caulk to fill gaps, you're probably missing something in the prep or measurement stage. Better to spend extra time shimming and adjusting than patching gaps later...caulk's a band-aid, not a fix.
Fair point about caulk not being a substitute for proper prep, but I'd argue it's more than just a band-aid. Even with meticulous measuring and shimming, you're dealing with materials that expand and contract over time. A quality caulk or sealant provides flexibility and weatherproofing that shims alone can't achieve. I've seen perfectly shimmed windows still develop tiny gaps after a few seasons...so I'd say caulk is less a shortcut and more an essential finishing step.
