If the engines are well taken care of, they'll last a long time. I saw someone with a new beetle I think it was on here that the odometer just hitting 300k!!
The replacement motor that I ripped out of my car and replaced with the original AEG (see my build thread for info) had somewhere in the neighborhood of 190k on it.
Watch for some potentials of oil consumption, certain build dates of the AEG's had it, others didn't but that's extremely hard to tell when exactly it happened. Mobil 1 5w30 should be fine. As you creep up to the higher milege, maybe 200k or so, maybe try some 10w-30. A bit thicker so it shouldn't burn off as bad and still seal up everything nicely. Now if you debate between synthetic and regular oil, that's all personal choice and research YOU need to find. I know mechanics who swear by synthetic and others that despise it, all personal choice and knowledge basis.
Oh and when you do your next timing best, make sure to get the water pump that has the metal impeller. I've had a plastic on go out on me only after 15k miles yet I have the original ORIGINAL one the motor came with still intact after 161k miles!
You'll be very happy with the reliability of the motor and good luck with it. Ever have problems, don't be afraid to ask around here. We're a friendly bunch.