Re: How long can a MEV function ?
Probably the five year thing is a compromise between "long enough contract that you don't do very many risky docking procedures during its life" and "short enough that the owner of the client satellite can be assured that other than lack of fuel the satellite is otherwise expected to remain fully functional for the term of the contract".
Satellites are built for a certain design life, and stuff like solar panels, batteries, etc. will slowly degrade over time so you can't keep a satellite that's run out of fuel functioning forever this way. But perhaps after five years Intelsat might decide to renew with MEV-2 for another term, if their satellite is still functioning well and there is still a need for what it is doing.
Once Northrup feels more comfortable about the docking/undocking stuff they might be willing to accept shorter terms than five years.