Based on my experience packing lunches for my parents and younger siblings:
First, institute a 'no throwing anything out, at all, ever' rule. Yes, this means they're bringing home orange peels, but it has 2 advantages:
- You eliminate the risk of thrown-away lunch containers/thermos lids/sandwich bags, especially if they're re-usable. BIG bonus.
- You see what is uneaten at the end of the day. For example, my kid brother would throw away everything in his lunchbox. When I started unpacking the 'nothing thrown away' box, I saw that the granola bar was always in there. Because he didn't eat them. But he'd throw one away every day. ARGH. But if I hadn't asked for it to come home? He would have kept doing it. Similarly, a kid who doesn't empty his lunch box might need less food, but one who continually eats everything in there might need more. It lets you evaluate changing needs and what actually gets eaten, basically.
Secondly, I personally don't recommend any lunchbox that can't be washed and dried easily - everything spills, and it gets gross. I've had decent luck with old-style LLBean lunch boxes (especially in darker colors, so less staining). They're pricier, but they last. On the slightly less pricy side of things, Lands End has some decent ones that lasted more than 2 years (and are currently on huge sale...) . Both companies have decent warranties, and LL Bean, specifically, has a great reputation for honouring that, so if they don't last as long as you'd expect, they'll fix that for you.