What is your preference on a 30 year old FA to be? I know the circumstances matter, but in general, do yo always try to resign a player if they are the best option at the position even though they will start declining soon? Or would you rather go with a cheaper younger replacement that might not be as good, but won't be much worse. And if you do decide to replace the older player, do you try to trade and get as much value as possible, or do you value those Comp A picks more?

As you say it depends on a lot. But if I have a suitable replacement then I will lean toward the younger guy use the extra cash to fill another need, assuming you have any. As far as trade or take the picks, put it out there that you are willing to move him and see what you can get. If its better than a sandwich pick and a 2nd rounder Id move the guy.

the circumstances matter

https://www.whatifsports.com/hbd/Pages/Popups/PlayerRatings.aspx?pid=6322547

Would you resign this guy no matter what knowing he will begin to decline?

It depends on the rest of your team. If you need his level of production to contend THIS YEAR, you keep him, let him play out his option or just try to trade him near the deadline to a team that needs a rental. If you suck and will suck for the foreseeable future, dump him to a contender (play them all off each other to get the best deal)

IT'S JUST LIKE REAL LIFE BASEBALL.

Depends on a lot of things but I probably would resign him.

It also depends on the makeup of your league. A league with active owners will have contenders willing to partially mortgage the future to get this guy, plug him into LF (he isn't a legit 2B), and give you a player (or two) who might be a season or two away from the big leagues. You might even tell everyone what this guy's salary demands are long-term (if they're somewhat reasonable) so they can judge his 5-year outlook.

But with his ratings and makeup, as long as you have your training budget pretty high, he should stay the same for another 3-5 seasons minimum

for a guy like that I would typically want to keep him for 3 more seasons. If he is asking for 5, let him leave, that's way too long. If he's asking for 2, sign him for 2 or maybe add year 3. If he is asking for 3, I'm definitely not adding seasons 4 and 5. Longer does not equal better.

I ended up signing him for 4 years with the 4th being a mutual option. I figured I can still trade him if I need to