Rheem element change

My daughter is complaining about a lack of hot water recently, so i thought I would start with a flush of the tank. The water was cold. No rust or debris came out, the water was clean from the start. Can I assume that if the water drained out cold that the lower element is blown? The tank is about 10 years old, is it worth changing an element or should I just change the tank completely? I have done a lot of work here and have a fair amount still to do, if I can delay the tank a year or so, it would be nice, but if it is better to change it at 10 years of age I will. The other Rheem for the upstairs bathroom, of the same vintage, went 17 years and still work but the insurance company insisted it be replaced.