At what point of incubation have you had an egg explode? 1wk, 2wks? Older?

I have 8 shipped eggs under my broody on day 9. I also have three wouldn't fit under her in an incubator. I've been candling the three in the incubator and finding it harder than expected to tell what is going on in the light brown shells.

There is no point disturbing my broody till it's at the point even I can't miss what's going on but since the eggs were shipped and I had one broken and found a hairline crack in another one in the incubator I have a good chance there are eggs under her slowly going rotten.

So my question, how far into the incubation do they become a risk of exploding? Our weather is quite mild here being the first month of spring.
If I wait till 14 days is the chance of a mess still quite low for both oozers and exploders?

 

Because every second thing you read goes on about exploding rotten eggs.

I started to candle them when they arrived but I couldn't even tell if they had an air sac and all I could see was that the yolks were floating up and down everywhere. I decided I was probably doing more damage to already shaken up shipped eggs to no benefit since being a first timer I wouldn't be confident enough to throw out ant anyway. So thought it best to wait till further along and less chance of me getting it wrong or damaging eggs that needed air cells to reattach.

In the incubator I had one cracked that's done nothing, one very red with a distinct blood ring round the middle which I've thrown. From reading online I'd assumed these were the type of eggs likely to go rotten and weep or explode. As I've had two out of three in the incubator stands to reason there is possibly another under the broody.

I'm still useless at candling though so just checking its safe to leave an egg that is a quitter or has a blood ring under a nice warm chook for two weeks till I can see it's got a big dark thing in it so likely okay. I don't want to leave them that long though if a non viable egg will go rotten that soon and weep all over the other eggs or worse still explode.

 

Thanks. Puts my mind at ease a bit. Have also been thinking time of year could also affect the chances, middle of summer under a hot chicken would go off quicker than cooler days in early spring surely.