I'm definitely with the "it's not the stem seals" people.
Typically, if you burn oil right on startup, it's drained down while the engine is not running - as Rusper have said - but it's gone almost immediately but there's a general increase in oil consumption. Faulty stem seals (usually due to hardening with age and heat) don't really affect the engine's running to any great extent.
When you get oil burning under load, it's usualy coming up past the pistons, so if the cause is not something particularly unusual, I'm inclined to think it's piston rings. Shouldn't be appreciable bore wear at this mileage as you've said, so broken ring(s) as somebody else has suggested. This could cause bore damage though.
Sorry if I'm now teaching you to suck eggs but anyway this is the way I see it...
The crankcase is ventilated through hoses in the cam covers that attach to the induction system near the throttle body. It's normal to pick up some oil mist and this often tends to collect around the throttle butterfly plate, which is why you often see people here being advised to clean around that area with carburettor cleaner or similar.
Under hard acceleration, increased blow-by at the pistons past damaged seals at the rings causes increased crankcase pressure. This is vented through the same placew as before but carries more oil with it giving rise to the blue smoke.
You should be able to see evidence of this in the induction system around the throttle body, unless it's already been cleaned up by garages that have already looked at it.
At the same time, oil is drawn into the combustion chamber up past the damaged ring seals on sharp deceleration when the throttle is closed and there is a large vacuum in the combustion chamber. I suppose in an extreme case of failed valve stem seals, oil could also be drawn down past the valve stems at the same time. I tend to think this would give a "puff" of blue smoke immediately the throttle was opened again, rather than smoke while accelerating.
It's going to be expensive though, I rather think.
