I just did some minor updates to my sheet format, but every time I do a new drawing the old format shows up.
I have to right click on my sheet and select Properties and then reload the sheet before the updates to my sheet is shown.
I have never tried this before - what could be wrong? .. I have done updates to my sheets before without this happening. 
If I understand this, you have altered your sheet format and saved it. Have you also saved your drawing template file by performing a new save_as and overwriting the existing drawing template? Do that if you have not.