I have a Macbook Pro late 2011 and want to purchase a Macbook Air 2020. The newer Macbooks have internal hard drives that cannot be removed. In my 2011, I've replaced the internal HD at least twice. Is it an issue for anyone that the internal HD cannot be removed/replaced? How does the unremovable one hold out?
Did your 2011 MBP have mechanical HDs (that is, spinning magnetic platters)? If so, the SSD in recent MBAs should be more robust. SSDs don't have any moving parts and are much less sensitive to physical shocks. This means you don't have to worry about, say, a motor wearing out, a read/write head coming into contact with a platter, or your backpack falling off a chair.
One thing you can do to help extend a SSD's longevity is to keep an eye on how close to full capacity you keep the disk. Each memory cell in a SSD incurs some wear (I'm describing this in non-tech terms) each time it is erased or written to. So if your SSD is close to being full, look for files you can move to another form of storage. Doing so creates space and helps the SSD spread activities that involve a lot of writing and erasing, such as downloading OS and software updates, backing up iOS devices, streaming video, and managing frequently edited documents, across a greater number of memory cells.
Reading stored data, on the other hand, doesn't affect SSD memory cells very much.
Finally, here's one real world example of SSD lifespan: there is a 2015 MBP in my household that is still going strong with its original SSD. The machine gets daily, extensive usage. We're hoping it lasts until an Apple Silicon MBP with a decent variety of ports is released (fingers crossed!).