The following are typical of the guidance on this matter:
From teenwire.com's Ask The Experts column:
"...one study actually suggested that sperm count increases
with increased ejaculation..."
"...masturbating daily or ejaculating frequently does not
reduce sperm count in later life."
In an article by Susan Yudt on teenwire, which discusses
Masturbation Myths for both males and females:
"...some people worry that masturbating frequently will
affect a girl's fertility or a guy's ability to produce
sperm. It doesn't. A guy may find that he has less volume
of semen if he ejaculates frequently, and his semen may
contain less sperm. But that doesn't mean that his sperm
count will be reduced in the future. The testicles produce
and store sperm beginning at puberty, and sperm production
continues through most of adult life."
And, from the Sexual Health Network:
"...the more ejaculations you have in a relatively short
period, the more depleted your sperm supply is. In general,
sperm levels reach "normal" after 2-3 days but, as you said,
there are times when it might take longer. There's no magic
mathematical formula for how many times a week you can
ejaculate and how it affects your sperm count: The more
often you ejaculate, the longer it will take."
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Additional information may be found from an exploration of
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Searches done, via Google:
masturbation sperm count