It’s a mandated 5 but recently was pushed out to 7 years of software & hardware support for Apple phones & computers. In some cases it can be up to 10 years.

If an Apple Store has the parts they will service your device. If they don’t they often times know a local shop that still holds inventory for old parts.

https://support.apple.com/en-us/HT201624

You can use a stylus currently with the MacBook trackpads & the surface area is big enough for signatures which I often do as well for work. This is the only “touch” use case I can think of for a regular laptop user. iPads exist for a reason & fill the “hybrid” niche well IMO.

I’m against touching my Retina display at all costs as fingerprints drive me crazy. If Apple can come up with a better oleophobic coating then what they use on iPhone for the display I’d maybe consider it but still find it unnecessary.