If you are going for the date method then you need to ensure that each date is a progression on the date before. 15 mins to an hour doesn't really give you much indication unless they have been fighting and need it done really slowly. Ideally, the longer the time the better if you are actually actively bonding, and each day the time needs to significantly increase.
You can't put them together and leave them unsupervised when you're away. You're just not going to be able to date during that time.