Three 4-year terms. There’s a learning curve, and at some level they’re operating at a disadvantage with respect to the permanent government bureaucracy.
Too long. Two three year terms for the house, two five year terms for the senate. Make them fund their own retirement like most of the rest of us, and participate in Obamacare and whatever other schemes they force upon the rest of us.
And require all political contributions to be anonymous. You can't sell influence if you don't know who is buying. Prison terms for violators. Unspent campaign funds go towards the national debt.