It depends.
If you're planning on being on reserve you need to be two hours away, in traffic. At a larger base (LAX, SFO), you need to be at the parking lot at about the 1:40 mark at the latest, and that's pushing it. You can (used to be able to anyway) check in on your phone. Probably safe to do that on the parking bus but it's risky to do it while still driving, if you get in a wreck or break down they will consider that you lied when you checked in.
Report time is normally one hour before departure (technically inside security, but not really enforced), show at the plane :45 prior. You can get away with :30 prior at the plane. But a reserve can get burned two ways...
1) The flight is already delayed for crew, and is fully loaded with crew and pax minus you and the CA has everything ready. If you're not at the plane at 2:15 after the call, it gets awkward.
2) Your first leg is a deadhead, and they are holding it for your arrival. That will become painful if you are not at the gate 2:15 after the phone call. This is worst case, and if the DHD leaves without you, you're in big trouble.
They are reasonable, if you have unusual traffic/road closures or the car breaks down it's no big deal. But if you make a habit of being painfully late due to normal traffic on your route they won't put up with that.
The smaller (maintenance bases) typically have employee parking lots a short walk from the terminal. At those if you get to the parking lot within two hours, safe to check in as you set your parking brake. Should take less than 15 minutes to get to the plane from your car.
If you're running late, DON'T check in until your car is parked. Again if something happens, that's lying which is really the one way to get fired at SKW (or most other airlines). CS will call you ten minutes after the missed check-in, just fess up and tell them when you'll be there. They typically won't document a late show as long as the plane leaves on time and you have margin of error for that. Again the bogey man in the closet for reserve show times is a deadhead... they might or might not wait for you.
If you're planning on getting off reserve quickly and just sucking it up until you hold a line, then you can drive as far as you want. I did five yours briefly at one point but that was too long and would not have done long term. 2-3 hour drive is pretty reasonable, but driving for hours in bad traffic is fatiguing. Also consider early show and later finishes... can you wake up at 0100 for a 0430 show? Good with starting your drive home at 2355? That depends on your personal tolerance, and also on the type of flying... a long, multi-leg day would suck if you had to get up at 0100 to drive in. When driving home late at night, if you're nodding off STOP, pull over and take a nap, or get a hotel. Had a classmate fall asleep and die on the drive home after a very long day.