need 85 gallon tub fill. Tankless for tub alone; add mast bth and laund., or whole house ?

[bikeboy]

Presently have 2 - 50 gallon tank type water heaters. one for kitchen, and two bathrooms; the other for mast. bath, and laundry; opposite ends of house (40ft. apart). I've posted a question in reference to this a while ago, but may want to update question. Should I install a small tankless just for tub; or general area of tub,master bath and laundry along side of existing tank heater, or eliminate both tank water heaters and install larger tankless with circulator for whole house? Since there's only two of us using hot water, I was told circulating hot water , even w/ insulated pipes and therm./timer; would be a wasting energy, and overwork tankless operating mechanisms to ware out certain part quicker than normal trying to keep up temps. I'm trying to figure out which option would best. I'd still keep one tank heater on stand by as a backup for tankless needing repair. The simple solution may be to either install a gas unit just for tub, in junction with electric unit, or replace w/ a gas unit.

Please reply;

Thank you;
HR...