Normally not... but it serves no useful purpose, and certainly doesn't "help" the engine any.
Specifically, valve float is when the springs aren't providing enough tension to allow the
lifters to continue in constant contact with the cam, so you are no longer gaining any rpm.
(We'll ignore "controlled valve float" experiments and associated research, for the moment)

Best case, you aren't making any more power than running in the proper RPM range.
Worst case, if allowed to achieve valve float frequently, or for long periods of time,
you will beat the cam and lifters to death in short order, at the very least.

(Not to mention that, being outside MFG's high RPM specs, you're probably killing everything else, too)