zip2play

I've taken Norvasc short term (a month)...I hated it.

Since it controls power and rate of heartbeat, I'd definitely wean after 10 years, although I had no symptoms cold turkeying after only a month.
On the other hand, some of the metabolites have HUGE half lives and may ween all by themselves.

Both drugs should be expected to have the same effect on BP according to their respective company's literature.
Maybe a good idea would be half dosing of the two drugs for a couple weeks and then a transfer to the Diovan full strength.

Let me add thoug that Diovan is slightly MORE expensive than Norvasc:
Diovan 160mg: $49.99/ 30 days
Norvasc 5mg: $42.99/30 days

Those dosages are comparable and the prices are probably the best available in the USA.