Suggestion

Having movable spawners that allow for unlimited spawns is kinda unbalanced as once a player has found a spawner and aquired some spawn eggs, there is no reason to go out and fight those monsters anymore.
But spawners are only very rarely found in the wild, so I think making spawners expire is way too harsh and players will start to accumulate more and more spawn eggs unable to use them in spawners due to the limit. Like this it is completely useless for any kind of farm and for what use would you want to use a spawner function like this other than profiting off the spawned mobs?

I think setting a limit to spawn eggs instead would be a much better solution as you can build a farm around the spawners you found and every time you manage to get a spawn egg, you can use them to do a limited amount of easy farming.
Unlike spawners, spawn egg drops are a renewable source and you can basicly set the ratio of "go exploring/fighting" and "farming at home" by adjusting the spawn egg rates.

This could be achieved by either not letting players remove an egg once put in in combination with the spawner keeping the egg inside when mined or letting eggs have their remaining spawner amount stored inside when removing/dropping a used egg before it expired.

Related to #93. and #92.

In a sense, I remove the egg inside the spawner to circumvent your exploit (#92). An idea is to make the egg still be consumed when the limited amount reaches 0, but when inserting a new egg, it will restore the limited amount. Then the spawner block will not expire and you have to find more eggs.

The problem with #92 still exists tho

I agree that this mod is OP depending on how you set the mod configuration. However, some people might only use the limited spawns feature, and disable the rest, which makes the mod act a lot different.

I think setting a limit to spawn eggs instead would be a much better solution as you can build a farm around the spawners you found and every time you manage to get a spawn egg, you can use them to do a limited amount of easy farming.

I like this idea.

im not a mod dev so idk if this is easy to do but what if when you silk touch a spawner, it saves the meta data into the item to avoid the exploit? and maybe has a tooltip to say spawns left: 3 or something. i think its possible but im not sure how you'd go about it.