If you're going to keep them all locally anyway, what's the point of IMAP?
(Admittedly my judgement was formed at a time when one user, one device was the rule. I suppose if mobile access to email is important, there's a good argument for keeping the data server-side. I solve that problem with VNC.)
I’m curious, do you log onto your computer from your smartphone in order to access your email?
Usually. If I'm going to be gone for more than a few days, though, I'll shut down the main PC and run Outlook from my laptop, which is set up to leave the messages on the POP3 server so they'll get copied into my master .PST file when I get back.
20 years means that either you maintain your own IMAP server and do a good job of it, or someone else does. In my previous company, there was always some reason why people couldn't put their hands on older emails. Meanwhile, my current .PST file goes back to 2007.
(Admittedly my judgement was formed at a time when one user, one device was the rule. I suppose if mobile access to email is important, there's a good argument for keeping the data server-side. I solve that problem with VNC.)