It's definitely an individual choice.
We have memberships at both Sam's Club and Costco -- Sam's is more conveniently located but we prefer the choices at Costco -- but we are a family of five with one in diapers (I think the membership fees are paid with the diaper and wipe savings alone.
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There have been years in the past where we have let our memberships lapse and would wait to renew them until we had some big purchase and could get a good deal with them.
Lately we have been renewing automatically, but I think next year we will be re-evaluating our Sam's Club membership again. We do save money when we shop there, but not necessarily enough to justify the fee, especially when we have a membership at Costco too and buy many of the same things (and more) from there.