Regarding the Holiday Tender, approximately how long would Chlor Discs in this last?

The discs themselves would be fully dissolved within 2-3 weeks, if the tender is completely filled. If no one uses the tub during this time you should still have chlorine in the water for up to one month. Be sure it is open to 1 - 2 - 3 slots. Never mix Bromine with Chlorine pucks.