Model save activation threshold should be reviewed

Description of the enhancement:

Currently, if a model has six or more users it will save after 600 seconds worth of changes, and if it has less than six, it will save after 60 seconds worth of changes. There are development-stage models with more than six users that would benefit from saving every 60 seconds. 

Example of the enhancement:

Could you, for example, change the "save every 60 seconds" threshold to be dependent on whether formula edits were made in a given time period rather than the number of users?

How this improves our business processes:

This would result in fewer models hitting rollbacks.