I am not aware of any substantial penalty for doing this, unless the methods you call are doing something computationally expensive.
By far the heaviest notifier I know of is the line_notifier - it can get fired 100s of times when you hit e.g. Shift+F3.
But, even then, you can simply choose to handle this at a later stage by raising a flag that gets picked up by the idle notifier.
This approach is described here, in case you haven’t already seen it 