To me, even the idea of them lasting 90 days is fanciful. I just don’t see them going. Not this group. Not this mission.
What’s missing is a decent propulsion system to get us to Mars in a decent amount of time, taking a decent amount of stuff along for the ride, or pre-positioning it.
Yeah I don’t see us colonizing mars till we can build really big ships in space that can be crewed by dozens or even hundreds of people. Larger crews mean less specialized cross training.
A support ship the size of an aircraft carrier could orbit as a small crew worked on the surface dropping supplies as needed.
Personally I think we should look at a permanent base on the moon first. The moon is easier to get to but is a considerably harsher environment which would be great for developing technology for use on mars.