well put . in industry the regs would get used 7 days a week 360 days a year and bottles changed many times over 5 years . home use 3 or 4 bottles in 5 years .If it's for personal use (you're a private individual using the reg at home, not giving it to an employee to use) then if the reg is in good physical condition I'd ignore the fact it's out of date. Especially as it's an inert gas not a flammable one.
I'm a qualified gas equipment inspector, and we have to recommend customers replace their regs when the date runs out to cover them and us from a legal point of view. But if you are sensible, and look after the reg (observe proper start up and shut down procedures) there's no reason you might not get another 5 years or more use out of that reg.
Of course, I accept no responsibility for the consequences of your decision, I'm just saying what I'd do in your shoes.