is the saying true

"there is no upper limit to the calories you should be eating when you are trying to gain weight"

is this true?

I am not a doctor but I would imagine there is some limit to how many calories your body can safely handle. Are you at any possible risk of refeeding syndrome? Have you talked to a doctor about eating to gain?

Am I right that you were planning to eat 4000 calories per day? If so that seems like a good amount to me - there is no need to go higher if you are gaining weight with that.

To a point..... If you need 4000 and you get 4500, no problem.  But if you needed 4000 and you were regularly eating 8000 you might find you started to get issues with indigestion and that could get very uncomfortable.

I also suspect that 'speed gaining' is a little like 'crash dieting'...  i.e. not all that desirable in the short-term or sustainable in the long-term.   Stick with a sensible amount and be consistent.  You'll get there quick enough, I'm sure.

That saying means that its OK if you eat 2750 when your usual goal is 2500, or 3310 when your goal is 3200. It means that you do not need to be entirely, hopelessly rigid with your daily caloric intake.

It also is to help remind those of us who end up needing tremendous calories to gain that is perfectly okay to eat more than the 2500/3000 minimums and not worry about it.

So, yes its true in that respect.

It doesn't mean that you should obtain abnormal and extreme eating habits to get there.