Thats weird, I wouldn't use softener for towels as that makes them go hard over time! (From my Experience) Though clothes I do use fabric softener.
I always use tablets, as they are pre measured, no over or under dosing, though I do perform a maintenance wash about once very 4-5 months, usually with a kind of Citric acid (you know hotpoint washing machine cleaner-the old stuff!) and occasionally with Bleach, and I run it on a cottons 95.
I do occasionally wash at 95 anyway with tea towels, though usually only wash at max 60C, and that's enough to keep it clean anyway.
Just use 95C once every few months and it will be fine.