As soon as we have inducted them, we can use them whenever we want, but of course during sanctions the spare supply will be stopped and the maintenance will rapidly become an issue. IN and PAF had faced that during Kargil, so you have to be aware of that when dealing with the US. It don't even have to be sanctions, but us not fulfilling their end user restrictions, would be enough to limit the spare supply.
Anybody who thinks that the US are now our friends, is simply naive and might have ignored the fact that they delayed the procurement of naval engines for our indigenous vessels, that they denied Israeli radar techs for LCA, that they wanted to tell us when and where to use the US engine in LCA...
It is in the interest of the US to get India to their side against China, just like it was in the interest of them to support Pakistan for decades against India. Whenever the situation changes, the US will changer their route towards us as well, that's why it's good that we remain cautions when dealing with them and that we don't buy all of their fancy stuff in big numbers, to make us dependent on them. Get specialised weapons and techs from them in smaller numbers (6-12 x C130J-30 for special ops, 22 x Apaches, 12 x P8Is) but skip them at the important deals (MMRCA, 5.th gen fighters, AWACS, tankers).