I've tried foiling and don't see the attraction. I prefer, by far, to run naked the whole way. So in my opinion, no, you aren't missing anything. As far as cook times, I cook St. Louis cut spares at 275 and am typically done in 3.5-4 hours. I start checking for doneness at 3 hours using the bend test, and then every 30 minutes after that. At 250 I'd expect 4-5 hours.