It was always easier for me to come up with the $$ to purchase a yearly combo than to purchase a lifetime which is always what I did till when I turned 65 (in 2015) and I bought the "old goat" lifetime combo for $25.00.
2017 info but I'm assuming this is still correct.....disabled vets get a reduced cost lifetime and the cost is based on your % of disability.
IIRC, bought mine in 1978, at approx. 24 y/o. Combination hunting/fishing was $225.
Saved $25 going with combo.
Bought my son his combo for 16 bday. Again, IIRC, his had went up a bit, $750 for combo. My oldest gson is now 15 but got him his early before price increase a month or so back. I think it's a good deal and especially worthwhile if like to hunt/fish.