Scheduled Refresh Time Selection Option

Currently we can only select 00 or 30 in minutes dropdown. Instead, if option is made available for selecting 05, 10, 15, 20 so on till 55, it will be very beneficial. We have one workspace where multiple reports are published. The reports are all scheduled to refresh at same time. The refresh currently takes approximately 15 to 20 minutes. But when individual reports are manually refreshed, it hardly takes 20 seconds. It will help to distribute load to server by selecting different times for different reports. As per agreement with clients we have to refresh the reports within set time but due to time delay, we have received few negative feedback from clients.