Welcome to Flyertalk and the EK forum!

Using your miles to upgrade is indeed the best use of the miles, this generally provides the best value in terms of $/mile if compared to the cash upgrade, due to the high carrier-imposed surcharges and taxes if you want to book an outright award. However be aware that EK doesn't always have upgrade availability, so check in advance or be willing to book now and gamble on availability opening up later. You can still upgrade at check-in if there are seats, regardless of upgrade availability, however if you won't be Silver anymore you won't be able to upgrade on-board.

Note that you can use expiring miles for redemptions/upgrades after the expiry date, but if you then cancel that redemption/upgrade you forfeit the miles.