I used to keep a life list as a young birder, but stopped when the attractions of heavy metal music and females of my own species took precedence - the last time I updated it was in 1982, following a period of time spent in South Asia which had temporarily rekindled my interest. When I travelled I kept a notebook to varying standards - some good enough to populate eBird lists, others less precise.
Fast forward to the early 2010s when I started to get back into birding, I was initially proud to say I had no idea how many species I'd seen, other than I knew it was some way north of 500....then 'just for fun' I started on the slippery slope of keeping a year list, initially just for UK, which since 2016 or so has been in public view in all its inadequacies on this forum.
I still haven't got a definitive life list. I collated my disparate notebooks using Scythebill and arrived at a total, but this year have started going through this more critically and putting the results - where I have sufficient information on location and date - on eBird. I still need to finish this process (including some of my more recent Scythebill / Bird Forum records), then add in the 'life list builder' species which can't be localised with sufficient precision. I'm hoping to complete this process before November (it won't be perfect, since it also involves an IOC - Clements transition to fit with eBird), as I'm planning to head for the Neotropics again and with it a chance to pass my first 1000 by the end of the year.
So is this process a good or bad thing? I concur with a lot of the sentiments expressed upthread - it's a bad thing if it makes your birding too target-driven, potentially diminishing the pleasure of observing birds you've already seen that year / in that location / in your life. Something that should be a simple pleasure becomes a source of stress and disappointment. And I'm admitting this as someone who (almost) never twitches rarities, and has thus avoided the more extreme swings of emotion associated with that activity.
Overall though, I'm happy I've become a lister again - eBird is a great tool, and gives you the warm glow of feeling you're contributing, however insignificantly, to a global citizen science project. Before eBird I was always really resistant to multiple lists for different administrative regions (my British list didn't last beyond my first overseas birding trip, aged 15) - now they're generated automatically I've got separate, albeit incomplete British and Portuguese lists, and can drill down into the latter and track my increasingly wide spread of regions and local council areas. This is of course another crazy rabbit hole to go down, and unlike patch listing, of no practical value whatsoever - but it does feed that urge to collect which is part of the motivation for listing.