Nice to celebrate Yorkshire Day with a pass for Speedy.

An eye watering 98 miles this year, I thought I may have beaten my previous record of 61 miles but clearly I have been over doing it.

I am pretty certain I last filled her up in 2013 and probably have enough fuel to last until 2018.

Well done.
Most years my 924 covers between 15k - 20k miles.

may pay you to shoot some fuel stabilizer into your tank if you intend using the car that infrequently ?

The issue with this modern fuel is exacerbated with a vented container, it also degrades in a full and sealed petrol container until all the water within the air has been "dried"as the ethanol which is hygroscopic absorbs the water content and grows microbes which can then cause, in extreme cases a sludge build up which on modern fuel injected engines should not be an issue, but on carburettor engines, much more serious. Returning to vented containers, all the above is valid except that because they are open to the air the fuel will continue to degrade in the same way, and further more many of the additives used in the fuel's production which help anti knock properties and initial short burn requirements, to aid start ups evaporate.

yep, we all have to a point but as they keep increasing the bio type additives into our fuel the shelf life is shortened. Good news for you is that the stuff you put into your car 3 years ago probably contained a lower level of bio's to cause a slower degradation.
The best solution for us is to use Shell V power which is the only fuel running 5% ethanol, which after discussions with Shell last year suggested that they were resisting the EU in not complying with the 10% and rising, addition of ethanol. Although they said that the pressure was on and who knows where things go within the next 5 years.

I had to fill her up today, on the way for an oil change at Tonbridge.

Should be good until 2020/21 Maybe