My only suit is a Botany 500 I bought from Men’s warehouse in the mid 90’s and the pants need to be altered. Have suits changed much since then? It’s your basic pin stripe.
I only need a suit for wedding, funerals and job interviews and I wonder if I should spend another $300 on a new suit or just have my old suit altered. I’m 49 years old.
I don’t think there’s an issue. I’m pretty much in the same situation as you, age, age of single suit and also what I need it for.
The only thing that I’ve noticed is that pant cuffs seem to have been eliminated in favour of a non-cuffed version. Unless you work with people in the fashion industry I don’t think anyone will notice anything; it’s good to be male. 
No, IMO so long as it is dark and doesn’t have anything really odd like huge lapels, and it still fits well, I wouldn’t feel the need to replace it.
The exception I would make to that is if you are applying for a job where there is a lot of public contact and the corporate environment is unusually style conscious.
Cuffs are still in. I’d be worried about giant shoulder pads.
SUITS are out of style.
Now if you show up dressed in flip flops and a Colts jersey, you’re well-dressed.
Frankly, I can’t tell the difference between suits now and suits in 1985, except maybe for wrinkles where the sleeves were rolled up Don Johnson style.
Guy who has to wear suits a lot checking in. Darker colours are perferred now and pinstripe (and waistecoat even) are back in fashion, from what I recall back in the 1990’s lots of colours were allowed.
Lapel Size.
Quasi
Oh yeah. Long Clinton-esque lapels are horrid. High and tight have been in for almost a decade.
As others mentioned your lapels and shoulders are most likely to make the suit look dated. They were screwing around with extra buttons then, but I’m sure your suit has 2 or 3. If you need it for job interviews and not actual jobs then it sounds like a new one would be a waste of money.