I was similarly getting through a chain and freewheel often, about once every six weeks or so, BITD. I began to use IGHs for all the hard miles, winter training, commuting etc. and derailleurs for racing and summertime touring. The amount of time and money I spent on bike transmissions reduced enormously.
I fitted a SA 5s hub ( a converted FW in fact) to my training bike on the basis that if it blew up, I could replace the innards with SA three speed parts. I even had a new internal sat there, lubed up, in a plastic bag, for years, but I never had to use it. Well that hub finally broke properly about three years ago when the axle (which was old when I started using it) finally cried 'enough' and broke in half. It had done about 35 years service by then (in my hands alone plus whatever it has seen before that) and had eaten between fifteen and twenty chains/sprockets in that time.
I normally let the chain go to about 1.5% and then change it and the sprocket. I find they last a good deal longer than on a fixed gear; I think that this is in good part because they can be run slacker (without problems) and this allows the rollers to 'climb' outwards radially until the pitch of the rollers best matches the pitch of the sprocket teeth. The slacker the chain, the lower the tension in the chain (catenary effect) and the easier the chain can assume the best position on the teeth. This means less roller movement on the tooth faces under load, and this means less wear. One of the things I am considering is using a single pulley to support the slack run of the chain (eg at the midpoint); I feel that this may let the chain run at even lower tension, so run more smoothly even when somewhat worn.
I've of course used many other IGHs too but the SA 3/4/5s hubs are still a favourite with me; simplicity is a good attribute to have, IMHO. Ideally an IGH should (I think) use a direct drive ratio for 'tapping along', have one or two higher gears, and three or four lower ratios. Ideally the ratios either side of the direct drive should be about 10" higher and lower respectively (so about 15% intervals). The lower gears can be spaced more widely apart, be less efficient etc and it wouldn't trouble me overly. Sadly few IGHs are made with this mindset and those which are tend to be expensive. Everything else is a compromise of some kind; choose your poison...?
Older SA hubs will accept two 1/8" sprockets and you can engineer a half-step system or a one and a half-step system, provided you are OK with using a derailleur. Arguably Brompton 6s gearing is an acceptable compromise; the tensioner is there anyway because of the design of the fold and the additional parts to double the gear ratios are not a major burden. If a non-dangling (cleaner, less easily damaged) 2s mech could be used on a large wheeler, it'd be a step forwards
cheers