I prefer paper copies. Keep them forever. Have a complete set of originals (no repros) back to 1931 with no gaps. I have a few repros from the earlier 1900's. Most are mint.
So to answer your question, I get 2 copies a year. One to read, and dog ear, one to keep for posterity.
I use the online versions for reference only. It's easier to stick a finger between pages and flip back and forth than to have to click thru the intervening pages. Especially if I don't recall what page number the stuff I was seeking was on.
A true collector!
Mine start in the early 30's, maybe a couple of late 20's. I can get lost in them. I also like good repos because old, even mint original 50's catalogs are starting to feel unstable. The paper on repos is newer.
Even though I don't collect anymore, I've found that the internet doesn't provide all the info needed. There is always the probability that the info manufacturers have on their website will be removed at some point, not to mention the possibility that the manufacturer closes shop. There have been times that I have missed items in the online versions of Lionel and MTH catalogs, that I noticed when I spent some time with the catalog in hand.
I'm glad I kept my K-Line catalogs.
I hate to see John at HSL having to quit selling his products. Much will be lost to the community. John did a wonderful job and a provided a great service to anyone that has an interest.