[Shalimar]

Very interesting thread, to all that's been said; as the owner of P337H, N64N I would add the following: It's an ideal aircraft for the mission that you describe but I do agree that thousand mile legs will put you at the limit of range. Certainly beyond my comfort level, but that's an age thing as someone commented.
Except for anything requiring penetrating the pressure hull, the pressurization adds little in terms of maintenance. The systems are small and I have found them to be very reliable. If you need to penetrate the hull, that's a whole new challenge, both to reseal if you are going through an existing opening or to go through the DER process if you are adding something like an antenna.
That said, I have found maintenance on the P's to be substantially more complicated than on a normally aspirated 337. I am an A&P/IA and do my own work and the engine compartments are crowded, almost nothing can be accomplished without removing other components and systems which, of course need to be reinstalled, but wait, while its out let's inspect and repair. A friend once remarked that the P337 has all the systems of a King Air without the room to work. It helps to be a watchmaker with the arms of a Chimpanzee to get in there and do stuff.
The pressurization system makes the aircraft very warm, hot in fact. You are sealed in this capsule and the compressed air from the pressurization is hot until you get to altitude. May not be a big problem in Denver, but it is in Phoenix where I fly. Once you are at altitude, it can get cold so a properly working heater is a must. The Janitrol heaters are another system that requires maintenance and is subject to an AD. No big deal but just one more system that requires maintenance and takes up front engine compartment space.
Insurance is a giant pain in the butt. Insurance companies must think that this is some kind of mini-airliner because they insist on recurrent training and the premiums are very costly, much more so than a non-"P". There is another thread that talks about this.
All that said, the P Skymaster is a fantastic aircraft. Great performance in a small package, relatively economical to own and fly. My recommendation is to find an A&P/IA who knows the plane to do a thorough pre-buy and to do your maintenance. Also consider attending a CPA 337 systems and procedures course, very valuable.
Best to you