We have two water heaters with dual anodes installed in 2006.
May I ask why you are using two tanks?
Many builders will buy 40 or 50 gallon tanks as they are commodity items at low cost. Most of those builders will not install them to reap the benefits of reverse return plumbing. Even if they do, the losses of two tanks is significantly more than a similarly sized single tank.
Determine your water heating requirements and source the properly sized single tank and then do the proper maintenance to keep that tank for a long time. Real conservation.