Wheel upgrade - but is it worth given the age of my bike?

As others have said, there should be nothing wrong with an 'as new' 2013 bike. Your bike shop was just trying to flog you a new bike!

Those a both decent wheels, but the Hunts will be more serviceable, if you can stand the loud freehub (I sold mine because of it!). Otherwise, talk to DCR wheels, Spokesman, Cycle Clinic, or any of many independent wheel builders, who can probably do you a lighter, stronger set for less than Hunt or Mavic. And they'll probably replace them free or at a discount if you crash or break them.

Personally I'd get some decent handbuilt alloy wheels from dsr, cycleclinic or one of the many good wheel builders. Personally I think discs are great if you remember to brake carefully, very easy to lose traction. I run both types. Group set wise I wouldn't replace until broken, but I'm a luddite when it comes to electronic shifting.

Why would you replace things that don't need replacing?? 2013 isn't that old especially if the bike hasn't been used much. I bought a new rim braked bike last year. Rides nicer and lighter than the disc bikes I own. And decent rim brakes do work fine enough.

So i'd say ride it, use it, if the odd component goes wrong then either search out a replacement on eBay or buy a new bike with discs etc then. And a new set of wheels with some nice tyres will not be a wasted investment. They're still selling bikes with rim brakes you know

I would say carbon rims can get a bit tedious when braking though. Don't work as well in the wet as alloy, can be a bit grabby in the dry if you don't choose a reputable set. £300 -£400 on some nice light alloy wheels and some GP5000s and you won't go wrong.

I would look in to build your own wheels if you are a bit handy. 

When I desided to uppgrade my wheels I build my own. Now I have build three pairs for my self an one pair for a friend. 

First pair the cost was roughly 400eur + the cost of a bunch of tools at about 200 eur.

My to first pairs weigh 1480g (shallow) and 1540g (45mm deep rims) and the latest pair I built weigh 1226 grams for the pair and the cost for that pair was about 930 eur inc delivery and taxes.    

Getting the know how and tha basic tools give you a lot of freedom when it comes to options.  

Plenty of cheap 6870 stuff out there, all my 6870 stuff is 2nd hand and works perfectly.

I can't necessarily comment on the wheels; I replaced mine with some handbuilt ones.

In these situations I'd see if you can find an independent bike mechanic where you can have an honest discussion about what's achievable with the budget available; they'd also advise on a strategy to replace components likely to wear out in the medium term.  Building up a decent set of components means you can swap them onto a new frame in the future.  Much as I will always support LBSs I find there advise is based around flogging you a replacement bike and the latest 'trends' (ie disc brakes); I can never have a conversation with a mechanic, hence I found an independent one.  Their labour charges sometimes aren't cheap but I've even sourced some components myself and got them to fit them.  Invariably when I've visited the indy mechanic there are some 'serious' high-end bikes in there being worked on so you know you're in the right place.  He still does the 'bread and butter' stuff sorting out bikes that have been rotting in a shed over a winter!

New wheels and new brake pads make a terriffic difference to an older bike either in carbon or alloy. There's no real reason to change the bike unless you yourself fancy a new one. There's no reason why your Di2 groupset should fail, they're made pretty well. Even if it does that might be many years away. You could always replace the groupset with a cabled one. That and I wouldn't buy a new bike just now anyway, good bikes are in short supply and good deals are hard to come by.

It is definitely expensive to replace 6770 DI2 because parts are somewhat scarce and other than the shifters it's not forward compatible with 6870 or the 8000 series. It's almost at the stage where it's better/cheaper to upgrade everything to 6870, which would cost around £400 from the secondhand market.

Your bike is likely to be fine in terms of frame integrity - it's aluminium so doesn't rust and is reasonably robust. And unless you're riding in winter or on poor quality roads there probably isn't the need to go with disc brakes.

Of the two wheels I'd go with the Hunts, simply because they're more serviceable than the Mavics. They use standard hubs, spokes, and bearings whereas the Mavics don't. And Mavic's future is still uncertain. Hunts will have good resale value if you do end up switching to disc brakes later.