You'll be very surprised at the condition of your lowers. Mine were trashed at only 77K miles. The UIM, however, looked excellent.
I agree with what you said about the upper bolts becoming loose. My upper was leaking coolant onto the lower manifold. So, I popped off the fuel rail and checked the torque on those bolts. All 11 were only at 35 - 60 in. lbs.
So, I retorqued them to 89 in. lbs. in the proper sequence, using the Permatex blue thread locker. Nonethless, I still have the leak.
So, looks like I'll be doing another UIM on it. This time I think I'll have it done (time is too precious right now) and I'll use a Dorman. Lowers should be fine, however.