Reddit user Mountain_Situation_8 has flagged up a way to save on PS Plus upgrade costs by stacking your regular membership for certain number of years, saving you plenty of cash in the process.
Essentially this involves stacking enough years of the standard PS Plus Essential membership (at least two years if you want to really benefit), and then paying the $150 upgrade for PS Plus Premium, which will turn out cheaper than if you were to pay the yearly subscription normally.
This also applies to the PS Plus Extra subscription, which comes with an upgrade fee of $100. How much you save also depends on what price you buy those years at.
The new PS Plus is now available in the US and you can view a full list of available games here.