In that case I'd consider the annual oil change a preventative measure, unless you use an oil analysis program. Reason, combustion products that make it past the rings and into the crankcase can become corrosives over time. Without at least once a month running of the engine, water can also develop in the oil due to condensation, especially in coastal areas like yours. This water will mix with the combustion products over time and cause the corrosive to develop. Alternately drive your Saab, mon and make this a moot point. :lol:
The problem would be water contamination and gasoline contamination. BUT if the car was stored, I don't think it would be a real issue. Oil sitting in the pan is just like in the bottle, the worst condensation would be the humidity in the crankcase but there is only so much water in there.
Now if you say drove 600 miles over the past year at 0,6 miles at a time, or 2 miles a day or something like that I'd expect more condensation and blowby contamination from the engine never getting hot to "distill" that stuff off. But then I'd expect the oil to look black or even starting to get the white water-soaked oil look.
Certainly if the car was in a barn for 20 years I would change the oil promptly. If the oil was at the proper level, even if it was black or something, I wouldn't hesitate to start the car and drive it out of the barn or even back home but I'd change it very soon. But in such a case, probably the main seal (if it is a rope seal) will dry out, and get spun out by the crank anyway necessitating engine repairs and if you changed the oil you'd waste it all on the ground anyway :lol:
But for 12 months I wouldn't be too worried... more importantly the Saab engine doesn't even seem to care much about oil as long as you have some oil inside and you have oil pressure. If you had a 9-5 I'd be more cautious but probably you could keep the same oil for 50 000 miles and the engine would still be humming like a sewing machine (I don't recommend this!)
I think another consideration would be how much you are going to drive. If you're going to make only another 600 miles it is nuts to change it but if you are going to make say 6000...