Cooking with propane

[Firstrmc]

Here's a question from my DW. She just used the oven to make her darling husband (that would be me) an apple pie. It was only a frozen pie so don't be thinking how wonderful she is but the directions said 60 minutes and it actually took almost twice that time. Is this normal or could there be a problem that we should address? We're used to cooking with electric so this cooking with propane could take some getting used to but we're just checking.