Tube Life: 6SL7; 6SN7, 12AX7, 12AT7, 6DJ8 et al

I've finally found a tube compliment that works well with my Tube Integrated and I'd like the tubes to last as long as possible. I've heard everything from turn your amp off when it's not in use even if it means turning it on and off a number of times a day - to - just leaving the amp on all the time.

Advice?

Thank you!