I would recommend you only use the attenuator if you have your recorder AND any preamp all at or close to lowest gain levels and are still at or close to brickwalling.
Although a good attenuator shouldn't degrade the recording, it's better if you don't need to have an additional item in the gear chain if really not necessary.
There's nothing wrong with running preamps and recorders with low gain, and in fact that would be preferred as in general the higher gain you add at those stages the more likely you are adding at least small amounts of noise. There are exceptions of course and sometimes beneficial things happen if gear is pushed to certain levels, but in general I would say this is a good position to start from.
Best to aim for about -12db or so during the recording and just raise in post-processing. If you push to the edge, and especially if in a situation you can't monitor levels closely, you run the risk of irreparably damaging the recording. Easy to add gain later. Not easy, and often impossible to fix distortion from overloading.