Firstly you said "temporary access" to the extra and premium catalog. How is it temporary? If you're talking about the games leaving the service, that doesn't happen with all the games. In fact it's a small portion. If they are Playstation Studios games they do not leave the service.

If you were referring to the length of time the OP will have premium then that still doesn't make any sense. He has a few months left of Essential. He pays $20 to access premium and extra for the rest of the time he has left. You do realize he could just re-up the Extra or Premium tier right? You do also realize he could just buy the game for $10 and still upgrade to Premium for $20 and enjoy nearly 1000 games (extra + premium). Your post suggested that paying $20 for the subscription is a rip off vs. paying $10 for the game, henceforth exaggeration. You can say you disagree with that I wrote but that's how your post comes across. If you meant none of that then please clarify?