"They're holding up fine so far, but now you've got me wondering if I'll regret not going full-frame down the line..."
Honestly, I wouldn't stress too much about inserts vs full-frame. When we bought our place, budget was tight, so we went with inserts too. Three years later, they're still solid—no drafts or issues yet. Sure, full-frame might be technically superior in theory, but unless your frames were already in rough shape, the difference probably won't be noticeable day-to-day. Save that cash for something more exciting...like plumbing emergencies or surprise roof leaks.
Yeah, inserts are usually fine unless your frames were already pretty shot. I've seen plenty of homes where inserts lasted 10+ years without any noticeable issues. Sure, full-frame replacements can give you a cleaner look and maybe slightly better energy efficiency, but honestly, the difference isn't huge if your existing frames were decent. Like you said, better to keep some cash handy for the unexpected joys of homeownership...