| I don't think the bikes will expire. Mine did 6 or 7 half hour sessions two days in a row in Spain and it was 20 odd degree's. Maybe some of the older bikes might experience some issues, Ali seems to be having some heat related issues with his bike.
It will just be the rider I think, if you can stay focused and keep your mental 'togetherness' you'll be fine. I don't think anyone is really going to taper off physically, because it's not overly physical work and it's only 30 minutes. As long as everyone stays fairly relaxed on the bike and remembers to breath that is!
I'll be disappointed if I finish outside the top ten. | 
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