Make changes for the business -
so the users can do their job and get out of the door at 5pm
Keep it running, until they replace it with a new one (someday!)....
And don't break it, never, never break it!!!
Avoid the polictics
Oh - its a trade settlement system for a large investment bank...
Previously supporting a crap BT system:
Keep it running, it would "run too slow" so restart it. 24/7!
Bad experience; worst system I ever saw