In reply to TobyA:
That is what "wetting out" means but people often associate it to failing. It is not failing. All that's happened is the straps have worn the DWR off. Without DWR, any and every jacket will wet out.
To "wet out" is the saturation of the outer (face) fabric of the garment. ie, no longer beading. The reason this is significant to modern garments, especially jackets, is that the breathability in wetted out areas is reduced to 0. Like us, garments can't breathe through water and wetting out is essentially waterboarding for your jacket. That's why DWR is seen to be so essential, as the beading allows the membrane in the garment to "breathe".
The reason I wouldn't worry about it wetting out where your rucksack straps sit is simply because the breathability is reduced to nearly 0 by having your straps there in the first place. Your jacket can't breathe through straps, so why does it need to breathe on your shoulders?
To replenish the beading, simply apply any "proofer" spray or post wash kit, like TX direct.
Only when your jacket gets wet on the inside, whether its from leaking or condensation through excessive wetting out, would I worry about the integrity of the jacket.