Did something similar a couple years back—old farmhouse windows with new insulated glass. You're right about hidden costs though, especially if the frames need repairs or wood filler. I underestimated the sanding and repainting time big-time... But honestly, the comfort difference in winter was noticeable, and it felt good to reuse instead of tossing them. Just gotta weigh your patience (and budget) against the payoff.
Did a similar job myself a while ago—replaced glass in some old Victorian frames. Honestly, the hidden costs and labor were more than I'd bargained for. Sure, the comfort difference was noticeable, but I found myself wondering if I could've gotten equal or better results with new, quality replacements. DIY reuse has its charm, but you really gotta factor in your time realistically...and patience. If you're up for the challenge, great—but don't underestimate the hassle.
Totally get what you're saying about hidden costs sneaking up on you. I tackled a similar project last summer—thought I'd breeze through restoring some old sash windows. Ha, joke was on me. Between scraping off decades of paint layers and tracking down matching hardware, it turned into a mini saga. Still, gotta admit, there's something satisfying about keeping the original charm intact. But yeah, if you're short on patience (or sanity), replacements start looking pretty tempting halfway through...