We did a trial of the bin size and four week collection in October 2019, and for most people it was the right frequency.
We know that in some households the bin for glass will hardly have anything in it after four weeks.
We also know for others it will be overfull (especially if you've had an event during that time).
If you find you have too much glass occasionally, talk to your neighbours about the extra space they might have in their bin, or you can bring up to 0.5m3 to the transfer station free of charge.
If you consistently have more glass than the bin can hold, consider upgrading to a larger bin.