Not contradicting ACA, but I personally, wouldn't have considered salmon an oily fish but I could stand corrected. Anyway, as a person who lives on chicken & fish & as such, buys those in bulk as opposed to red meat, I can tell you that the salmon will still be fine in 3 months time once stored in a deep freeze with a 3 * rating. Because you will be serving it to other people I wouldn't take a chance on it any longer than this. However, if it were just for myself, I've often used a trout or a salmon cutlet that has been in the freezer for 6 months and there hasn't been a bother on me after it.
Also, do you know what's gorgeous on it, even though you haven't asked and I know you're supposed to stick to topic on these pages - but the Schwartz jars have one simply called "Fish" and it's lovely sprinkled onto salmon, but you might want to try it on a cutlet first to see if you like it as it may be too strong for some tastes. Enjoy
salmon has a higher than 5% fat content so normally would be classified as an oily fish . The significance of this for freezing is that is has ta lower water content and is more susceptible to freezer burn. Once the salmon stays in the deep freeze and there are no temperature fluctuations it wont kill you to eat it after keeping it for longer than 3 months, the texture of the fish flesh may have changed and the taste may be a little blander.
I grew up in a salmon-fishing area and while one can't beat fresh wild salmon just out of the river (with minted fresh peas and new potatoes - yum!), I have often eaten frozen wild salmon after 6 months or more and it is still good.
One of my siblings used to say that it remained perfect for up to a year if it were put in a bag covered with water into the freezer.
A minor point, but there's am implication here that it would be somehow unsafe to eat after three months. Not so: the problem with long storage in freezers is more to do with degradation of the flavour/consistency of the food: once the freezer's working correctly, there should be no increased risk from bacteria etc. regardless of how long it's stored. Just mightn't taste the best....