I've seen it stated many times by those apparently expert, certainly
more so than I, that with electric heaters, the tank can last waaaaay
longer than the electricals.
Ask around locally as to how long heaters normally last with your water
chemistry. Ask the plumber how the tank innards looked when he pulled
What I'd do:
1) get a replacement anode rod, pull the existing one, and replace.
2) ditto with heating elements and t-stat. You may need wrench to fit
element. And proper sealant. Lotsa supply houses all over.
Sediment cleaning is good, too.
That might buy you 10 years more. If you want better insulation, have
no problem financing it now, and have suspicions about heater from
above, go for a new one. And ... much better yet: gas. Price/BTU
typically 1/4 of electrical power.