Unsure of how many hours a week to do?

I started learning at the end of February. I was bought a 10-hour package with a new instructor as a gift. I've now reached the end of the package and am moving into paying per hour - which is £40. I'm currently doing 2 hours a week.

I had a chat with my instructor about moving into doing either 2 hours every 2 weeks or an hour a week, as £320 a month at least (unless there's 5 weeks in a month then it's £400) is a lot of money in the midst of the cost of everything else.

He said he understood but that an hour a week is too little, and a lesson every two weeks isn't good for continuity.

I seem to be doing okay - very positive lessons so far. And I haven't been consistently doing 2 hours every week due to a couple of things that cropped up that meant I had to push back a couple of lessons (bereavement/hospital appointments).

So I'm just wondering what would be the recommended amount? Would 90 minutes be suitable if that were possible?