Subaru won't start

I have a well-maintained '99 Forester with 160k that has hesitated to start on occasion for the last 3 yrs. Usually, it would take 5-6 key turns to get it going, but seems to worsen in the warmer weather. I had discussed it with my mechanic a few times and he suspected the starter, and said “one day it just won’t start at all” if I don’t get it repaired. Last summer it was happening more frequently and I knew I didn’t want to end up stranded somewhere, so I decided to take it in.

Coincidentally, perhaps, it REALLY didn’t start one morning because the timing belt went kaput in a very bad way, causing all kinds of problems. I had it towed and they did “open heart surgery”, including a new starter, which resulted in a $2200 tab (my other option was buying another car, so I went for the repairs). The car had been running great for the last 8 months, until we started to get some warm weather & it decided not to start again. I had it towed to the shop, but they got it to start every time & couldn’t figure out the problem. A few days later, I drove the car home and had driven it daily for about a week until it happened again. It sat in a city garage and I tried to start it every day for a week with no success–and noticed the battery power was diminishing each day. My boyfriend decided we’d try to jump it and it worked (for the 30-min ride home). Totally dead the next morning. Could this be a bad connection to the battery? Something sucking the life from the battery? I appreciate any ideas!