There should not be a worshipping of manager, something that is a disease in the United fanbase. A manager should be sacked when stuff is not going well, and should be sacked quick.
Conte, most likely, won't be here for longer than two years. On his nine jobs in football, he has been longer than two years in only one of them, at Juve. He was there for three years. Having him in a short contract will be the difference between paying 10m in severance fee, or 30m. So yeah, if we can get him in an 1.5-2 year contract, it will be very good. Especially if we are not completely sure about him and there are better alternatives down the road.
For what is worth, I like Conte and I would like him to be here longer than the current season. But it is imperative to get him now, even if there are plans for a more progressive manager (that we cannot get right now) for the summer.