It is essential for every pilot to be not only current but proficient. Without practice skills degrade and can even fade away some day.
That’s why FAA requires BFR (Biannual Flight Review) for any type of flying and IPC (Instrument Proficiency Check) for instrument pilots who did not fly enough instrument procedures during the last 6 months. To be more specific, one needs at least 6 instrument approaches during previous 6 months to act as a PIC for flying IFR.
If a pilot do not have the required approaches, and it is less than a year since a pilot was current, it is still possible to fly the approaches under simulated instrument conditions with a safety pilot. Safety pilot can possess just a PPL without Instrument Rating since the flight can be conducted under VFR (Visual Flight Rules) in VMC (Visual Meteorological Conditions).
After a year if the requirements are still not met a pilot must pass an IPC with a CFII (Certified Instrument Flight Instructor) or a FAA examiner.
It is different in Europe where the Instrument Rating must be just renewed every year with an examiner. Another difference – in Europe during training of flight tests one should just fly under IFR, even in VMC without view-limiting devices like foggles or hood.
My FAA IR currency already expired, and I decided to regain my skills and pass an IPC. I still don’t have a EASA IR, and I have no idea where I can find a FAA CFI in Europe, that’s why I decided to fly to the US. It could be even less expensive due to flight hour prices.
What can I say about it? More flying is better! And it always pays off to renew theoretical knowledge. I greatly recommend to take some courses from https://www.faasafety.gov (a lot of them are free!) and use these books.
During all this ATPL theory preparation I really missed flying. So good to take off again!