Not urgent at all, just a minor suggestion:

In the benchmark scripts I'm currently running I want to limit the number of samples in a data-pipe according to an args.limit CLI parameter. I'd be nice to be able to just write:

dp = Header(dp, limit=args.limit)

and let Header be a no-op when limit=None. This might be a bit niche, and the alternative is to just protect the call in a if block, so I would totally understand if this isn't in scope (and it's really not urgent in any case)