My (albeit limited!) experience is that, as a rule, headset bearings do not catastrophically fail unless they are already so far gone that you can feel a really obvious graunch every time you move the handlebars......so......you will probably be ok for a bit.........(ish) They are 'THRUST BEARINGS' rather than purely rotary bearings so a different dynamic is at work.
But they don't fix themselves once they start to go. Catch it soon enough and a simple strip and regrease may suffice. Otherwise.....it would be a good idea to replace the headset/bearings/races as appropriate.
PS
However
None of the above implies a
guarantee of safety etc!!!!
HTH
w