So, for sleeping I'd go for softer plugs like those made by Howard Leight for shooting (Laser Leights) or Moldex Spark Plugs.

Hearing protection always talks about attenuation in terms of dB(A) (A-weighting being a sensible thing to do when measuring perceived sound levels). 30dB(A) is a significant attenuation (logarithmic scale, don't forget). 35dB(A) is quite an improvement over 30dB(A).

For long-term use, ear plugs aren't great. But ear defenders can be had cheaply which will work well; I know of some people who use ear defenders atop in-ear active-noise-cancelling headphones as a double-whammy.

The correct answer is to work/sleep in quiet places, though, but I realise this is fast becoming a luxury.