In the last couple of months I've noticed that there are certain time expressions after which the present simple or the present continuous converge and can be used withouth any change in meaning. Let me support my question with a couple of examples:
It's the last time I repair this umbrella
It's the last time I'm repairing this umbrella
When I make a salad, I always use clean hands
When I'm making a salad, I always use clean hands
I'm really confused as I can't find any grammar rule that would explain this curiosity. Perhaphs there isn't any. Any feedback will be much appreciated.