Cat on steroids for cat flu

[MushMonster]

I do have a beautiful Bombay boy.
He was very sick as a kitten, he had cat flu or a similar virus at the time he was adopted. After a good while at the vets, it subsided and he has been healthy for years. But the vet did say at the time, his problem may come back.
He has spent the last ten months sneezing and caughing. Then lots of mucus discharge from the nose. Eyes are ok. Mouth mostly ok.
He eats well, breaths ok, he gets a bit less active. The vet gives him antibiotics, he gets better for a month or two and then is back to square one.
The vet has suggested a long term of steroids, which he had for 2-3 weeks on his last relapse.
He is getting snotty again and it sounds like he may need steroids for a long term.
Does anyone have any experience on this? Any of yours recovered from chronic cat flu?
(Picture of the 3 of them chilling on some boxes)

He seems to be unlucky. He sneezes quite a lot.

@MushMonster I meant to reply to this when you posted and forgot.
1 of my cats had cat flu when he was a kitten, prior to us having him. He was left with chronic rhinitis and quite frankly when he sneezes he could replaster the walls . He has a 5mg steroid once a day and if it's particularly bad the vets will give him a steroid injection, and we've also found bisolvin powders to be useful for him. Apart from the snot and sneezing, he lives a completely normal life

Most of these are herpes or calico virus which become latent infectious which flare when the cat is stressed. There is a really study that found that the feline specific probiotic purina feline fortiflora increased the times between flare ups.

Thanks so much for both replies @Lonecatwithkitten and @Justonedayatatime11
I am rather worried about giving steroids long term, but that was what the vet said is likely to happen.😞
I am giving them all L-lysine with their wet food, apparently it helps to reduce the virus reproduction.
It is, indeed, likely to be the herpes virus and he is rather stressed at times (he is my late MIL's cat and the other two big ones fight him quite a bit- he is still the boss around food!)
I will check into the bisolvin and the probiotic. I was, indeed, looking into giving him a probiotic. Thanks so much!
I did clear his sinuses on Saturday with saline solution. It was not easy, but at present, though he snots, there is not mich mucus, so he can breathe comfortably.

Does the booster vaccine help? Do yours have the vaccine, even if they already got the virus?

@MushMonster the studies for that fortiflora was better than lysine. It does need to be that specific probiotic as other pet ones are not cat specific and not as effective.

I bought him that one from amazon yesterday. It should arrive soon.
Also, it looks like he will be getting another lot of antibiotics and steroids this week 😔