Not an electrician, consult a real one for any actual electrical work or questions.
It's complicated. Heat builds up over time. So for example your standard 15 amp breaker on a 14 gauge wire in the US is rated for 15 amps of intermittent use, but if you draw that continuously without letting the heat dissipate it becomes a fire hazard. IIRC circuits are generally rated for ~80% of their max load for continuous use, so that 15 amp circuit is considered good for 12 continuous. Or in your 10 amp example 8 should be ok.
Your oven and circuit should be sized such that your long cooks aren't a concern, if you look at it's label you'll probably find it has a max draw of well below 50amps, but if you have actual doubts ask a professional.
It's complicated. Heat builds up over time. So for example your standard 15 amp breaker on a 14 gauge wire in the US is rated for 15 amps of intermittent use, but if you draw that continuously without letting the heat dissipate it becomes a fire hazard. IIRC circuits are generally rated for ~80% of their max load for continuous use, so that 15 amp circuit is considered good for 12 continuous. Or in your 10 amp example 8 should be ok.
Your oven and circuit should be sized such that your long cooks aren't a concern, if you look at it's label you'll probably find it has a max draw of well below 50amps, but if you have actual doubts ask a professional.