I stored some bulbs in the fridge a while ago. Now it is already the 50th day. I am wondering, if I store it longer than the recommended duration (60 days), would anything happen to them?
Yes, I should think so, but I suppose the success rate would vary depending on what kind of bulb it is. Bulbs contain the food or nutrients to keep it alive while it is dormant through the winter. Sixty days in the fridge is shorter than an outdoor overwintering and definitely cool enough so they should be fine.
If the bulb is too squishy it might have started to rot, or if it's crispy it might have died. Otherwise I think they have a very good chance of germination.
Last year, I stored tulips and daffodils in the fridge from September until January. I only got one daffodil to bloom (but the weather was VERY flip-floppy last year which confused my entire garden). However, the tulips all bloomed incredibly (it was perfect temperatures for them when they were busy blooming).
My conclusion is that your bulbs will be fine.