As you can see, people deal with progression in many different ways. My husband is 220 pounds and I will no longer put him on a stairlift by myself. If your PALS is small and CALS is strong, things are much easier. Some people, like my husband, crave that shower and others don't find it worth the energy (and I'm sure things will change for us as my darling gets even weaker). I would say that you need a plan for being downstairs, and you need to be prepared to make that move at any time. If the shower is the big problem, there are also portable showers that can be set up in the house or even in the garage.
Many people make modifications to the house and later decide that they were not worth the time and money. If you don't, as you can read here, there are many ways to get around it and still be downstairs. You must decide on your priorities. We LOVE the wet room shower, but we also had the resources to do it. My husband is 2+ years in and on a slow progression, so it was well worth it to us. What I would really NOT want to have happen is to have a PALS trapped upstairs. If he/she wants or needs to get out of the house, will there be strong enough people to deal with the chair lift once those core muscles are gone?
Becky