Also, the passenger elevators manufacturers for interiors is much better in this case. One can access the upstairs at will and it is even feasible when people are tired when things are to be taken up and down.
The average time taken for an installation to get completed is around a couple of weeks which includes the making of the rail and the customization of the lift to land above the stairs.
If you need to save money here, then it is not worth to have a stairlift installed in the first place. Many people are also okay if they need to walk a few steps for reaching the landing platform.
A sort of u-bend would come when they turn at the top especially when they reach the landing of floor. The time to install a curved one is much more than that of a straight stairlift but the speed in which a curved stairlift can be installed altogether depends on the company which is hired to do the work.