I do single engine stuff, alternatively General Handling and IFR (real IMC if possible), to keep the hours ticking over, plus the odd jolly flight VFR. Having a share in an aircraft helps.
I then go to a piston twin simulator fairly regularly to keep up the multi-IFR skills ready for that sim ride or IR renewal. The one I go to (an old but functional FNPT(G)) is almost a tenth of the price of the real thing so you can see the savings.
cheers!
foggy.