Is 145 Y.O. centerfire ammo collectable?

Yup, lots of collectors of that stuff. I myself collect metric-military rounds from the 1880s on up.
Let me know if I can help. Post some pics.

They are very collectable. And like any other collectable, condition and originality are important. Do you know the caliber of any of the rounds? Any head stamps? Any packaging, an old box perhaps? If any of the rounds are grungy looking with lead bullets that look like they have been coated with a whiteish powder...LEAVE THEM ALONE !!!

Like jonnyc has requested, need some pics.

Here is an example of what I said. This is a rimfire round for a Spencer. Don't know which caliber, there were three or four different Spencer calibers and the all looked alike. Note the grungy copper case and the whitish look to the lead bullet. If I were to shine this cartridge up and make iut look pretty....It would destroy its value.

I gave my old stuff to my brother who has a fairly wide range of different cartridges, and original boxes. I gave him cup fire, rim fire, pin fire cartridges of various calibers and types. Some can be rare and valuable, just like any other collecting field. If you have a bunch of it, you might want to buy a book on collector ammunition. Books can be had used at a bargain price on various sites like eBay. Gun Broker has a collectable ammo category. One of the cartridges I gave away to my brother was a Winchester in 50-95. It was found by a friend of mine when he was a kid growing up in Wyoming. There was a cabin that burned down during and Indian attack as the story goes. While kicking around the place he removed a loose window cell finding 6 of these cartridges that had dropped into the wall. Truth of the story seems questionable but he gave me one, and in great condition so I was glad to have it, and the story is fun to tell no matter what. Original boxes can be worth more that the content at times, so treat them gently.

Ammo from the 1870's and 1880's is pretty rare. Collectors are always looking for ammo from this time period to mate with guns they have from the era. Value is dependent on condition and packaging. Boxes of ammo from the period are worth $100's.

Got any pictures?

Some of it is. You need to look at auction sites to see the selling prices
If you ever find any 6mm Navy Lee ammunition cheap buy it. That stuff is crazy expensive

Everything is collectable--to the right collector.

Century-old ammo is often simpler than arms it was meant for. If much like everything else in life, in a non-uniform sort of way.