Your freind gave you some good advice!
As @Beemer said, ID is perfectly safe for your leather. It's best for light cleaning and maintenance, if that's what you're after.
But to confirm, when you said "Leather Detailer," are you also asking about Leather Conditioner or Leather and Interior Cleaner? The former has some mild cleaning agents, SPF 65, and leaves the surface looking great. It's not oily, either. It also smells awesome! The latter is a heavier duty cleaner that should also be followed up with the LC to recondition the leather.
I use LC every couple months on my daily, but you could use it more or less often than that. Some leather needs more than others. Quite a few Vette owners on here... @Rich being one...that could attest to how often he applies it to his.