Is movement in my bottom bracket an issue which requires attention immediately? TLDR; my bottom bracket has movement when it shouldn't but no other issues / sounds / clunking. If I'm riding a few miles a day, is this likely to break catastrophically, or will it last another year or two issuing the odd warning sign?

This is different to the question: Riding on a failing bottom bracket - what could possibly go wrong? as mine doesn't experience clicking.

I have an old (20 yrs) mountain bike. The bottom bracket has play in it, one side can move up and down 1-2 mm - I am guessing this is simple wear. 

There are no other issues, no creaking, no stiffness, other than the movement. 

I cannot replace the bb unfortunately, tried to remove the crank arm and it pulled the thread out instead of the arm! I also suspect I'd have issues getting the bb out too. Bike is worth next to nothing, but this is an advantage as it makes it less likely to be stolen. 

Assuming this is simple wear, will I get warning signs before it dies, or will it just unexpectedly die on me? 

I understand there is no definitive answer to this, given the lack of info/data on the issue, but would appreciate answers from those with experience of this.

Edit: this is a sealed unit, so one side screws into the frame and the other has a plastic screw(?) to hold it in place. No adjustment of cups is possible as far as I am aware. 

To clarify, there are no sounds coming from the bottom bracket.
I'd suggest you try tightening the Non Drive Side cup and see if there are any improvements. 

You don't even need to remove the crank for this.  The right tool will just slip on, or you can get away with a big spanner and some plumber's sliding jaw grips.

If this helps the problem even a little, a proper clean and regrease will help a lot more.



The risk in not doing this is that there will be damage done to the cones in your BB, and if metal flakes off the inside surfaces where the bearings run, then its toast and you will need a replacement.  A cartridge bearing is relatively cheap these days, and is well worth doing even on a beater bike.