I have gone all four days many times in the past. If you plan 2 days, do one day in the stands and spend the cash and get a pit pass and walk around the other day. Traffic is really bad on Sun, so do not plan on getting out of there quickly, either hang oput a while or plan another day. Jump seats are usually tight in and out of Reno and Sacramento is much easier. The final Sun race comes down to who is still in the race (mech) and can be a blow out some years. Have fun!