Yes, having that last day cost less and less token could be nice. While Rory is right in things calculating but since you always loose some time between finished building and starting the next so it'll move into race time sooner or later and during the day there's more important stuff than timely managing of browser game buildings. So maybe not a must have feature but definitely one that'd be nice (and one that might make me actually spending a token or two for speeding up buildings).
Michael
Whats the best wat to invest tokens except structures?
In a competetive league buying extra engines to have a fresh one for each race is a must.
Not that far in the future you should want good drivers from your youth academy. Every scouted candidate costs one token and once you found one matching your criteria promoting him, or her, into your team costs 15 token. Depending your luck and how picky you are both can add up to 25 token per driver quite easily, so keeping at least 50 token in reserve for 2 new driver isn't a bad thing.