Cage set up for older rats?

My two older boys, 2 years and 1.5 years are in their own cage now, since the oldest one despises the younger ones and he's gotten really stressed out by them. I also notice his back legs slowly starting to go, no sign of paralysis or anything yet but he's starting to slightly look like he's tripping over his back legs or like they aren't working quite as well and his back end seems thinner. I have them in a cage now that is more floor space and opposed to ramps and etc. They have a hammock but never use it, I think because they don't like climbing so much anymore.

Since the hammocks don't seem to interest them, what are some other ideas and safe ways to keep them happy and entertained? I have a hut for them, they have 2 huts. I'm going to look around at some of the pet supply stores to see if I can find them a tunnel again. They loved their old one but it got so old and smelly I had to throw it out.

Any other ideas? I feel like they must be really bored and I want them to be happy old men. <3

Definitely look for low to the ground hiding places. You seem to get the idea with huts and tunnels. I found that my old men would only use hammocks if they were a cube/hiding hammock, and they were placed low to the ground (basically touching the floor).

Also, if they like shredding things give them some paper toys. My current rats LOVE newspaper, but then again they are all relatively young. It makes a huge mess but it keeps them occupied. Also, foooooood! What rat doesn't love food? Maybe make a pinata out of newspaper and some dry treats (like cereal). See if they are too old to bother, or if they actually go for it.

Lastly all I can suggest is lot's of outside of the cage time, even if they just cuddle/sleep. I loved my old men because they would stay put on my bed and snuggle. I think they enjoyed being in different sleeping places, because all they would do is sleep lol.

You can hang hammocks very low, mine like boxes with paper to sleep in and chew
Soft bedding changed frequently
If unneutered boys, check regularly for penis plugs

I like to use plain newsprint rather than newspaper that has printing on it. To me, it seems like the ink can both rub off and get in the air which I worry about since rats have such delicate lungs. I buy a large ream online of plain newsprint but you can also get a pad of it from an art supply store.

Do you older guys still like to chew? There are a big variety of chew toys you can get for them.

For tunnels, you can get plastic pipes from a hardware store or Home Depot. They have all different circumferences and lengths.

My rats love having new boxes placed in their cage. I always cut out "doors" on all four sides so they always have multiple directions from which to exit.

I love the idea of having them sleep in different locations. Just as Fumblesquid said, cuddling with them is a great way to ensure they get extra attention and variety.

This is the oldie cage I had set up for Dorian, my old lady, after the rest of her group passed on. She loved it Lots of snuggly beds, places low to the ground to hide, and low hanging hammocks.

I have always kept my oldies in the main cage, but lower and cover the ramps. I have always found that they continue to use the ramps even with limited mobility. I keep glove boxes from work (non-powdered, non-latex) so they can chew it up, pee on it, etc, and then I just throw it in the compost and put a new one in the cage.