That is a tough question. My battery life on my Palm Pre was ALWAYS terrible.
I had to have it plugged in constantly. I don't know if it was because my Pre's kept breaking and the refurbished batteries just didn't have the capacity of a new one or what.
For all of the complaining about the Evo's battery life, I haven't had any issues.
When I first got it, I made sure to charge my battery all of the way and then calibrate it according to HTCs directions.
I use Startup Auditor to make sure I don't have random crap starting up with my phone, and so that random apps like Qik and the Sprint apps don't open up randomly and sucking down my battery.
I use System Panel Lite to close any other rogue apps that don't close down when I exit them (looking at your SportsTap), but I don't use Auto Task Killer or anything like that.
I am a pretty moderate user, I have a Live Wallpaper and I browse the web a bit. I also play some light games like Doodle Jump and WordWise andsend out like maybe 20-30 texts, make a couple of short phone calls and my battery will last me 8+ hours.
Everyone is different though though so I guess your best bet is to use Sprint's 30 day trial and find out how the phone handles your usage, and if it doesn't last, then you can either return it or get one of those 3000mah extended batteries.