In the kind of things ill be making (disco lights / pinball machines etc) i would be happy if the chips lasted 10 years. The biggest heat problem i have will be my pinball machine. There are so many lights under the playfield and in the ones ive done in the past it gets quite warm in there but i dont think its enough to harm anything. The drive chips got hotter than the bulbs and they still work fine... except that one that was connected to the wire i accidentally shorted out :P The new one will be slightly ventilated anyway.

Is it just heat that makes a higher speed shorten the life? Could it be possible that doubling the speed doesnt make it heat up too much and so it doesnt shorten the lifespan much? (just a thought)

So, as long as theres no power issue (like running from a battery) and the lifespan isnt critical then using a faster resonator doesnt really make any difference? I suppose it does give you the chance to use that speed in the future though without having to solder a new resonator in