"Should they get re-baptized"s off-topic - it's opinion-based. However, here's a sample of what some teach and practice.
In various Churches that I've attended, including Baptist, Evangelical Free, and local community non-denominational Bible Churches, getting baptized again is fairly common.
This is based on the belief that Baptism doesn't save us, but is, instead, an outward sign of obedience to God.
In such denominations, the belief is that being baptized doesn't do anything to save us. Rather, it's a symbolic, outward profession of our faith, and our rebirth in Christ.
(Reference to back that up at Doing Baptism Baptist Style.)
In cases such as that, it's entirely appropriate to go through another baptism. Re-committing your life to Christ is perfectly valid, and to go through a ritual that symbolizes this is perfectly OK, but not required.
They don't see it as necessary because to these groups, baptism wasn't necessary in the first place.
As an analogy, to groups that see Baptism from this perspective, it's no different than renewing your wedding vows.
More specific to your question, there are several denominations that address this. For example, the La Vista Church of Christ has this to say in their article on the topic:
Reading the article makes it apparent that they believe that baptism does have an effect, yet they say that it's appropriate to do a second baptism, and also use the renewing of the vows analogy.
(I'd recommend the full article. This is just the closing paragraph)
Being baptized is compared to the Old Testament practice of being
circumcised. "In Him you were also circumcised with the circumcision
made without hands, by putting off the body of the sins of the flesh,
by the circumcision of Christ, buried with Him in baptism, in which
you also were raised with Him through faith in the working of God, who
raised Him from the dead" (Colossians 2:11-12). The very nature of
circumcision is an act that can be performed only once. Similarly,
baptism is related to marriage. "Husbands, love your wives, just as
Christ also loved the church and gave Himself for her, that He might
sanctify and cleanse her with the washing of water by the word, that
He might present her to Himself a glorious church, not having spot or
wrinkle or any such thing, but that she should be holy and without
blemish" (Ephesians 5:25-27). Marriage is for life. Some renew their
vows, but that renewal doesn't make the original vow of non-effect or
say that the couple was any less married prior to the renewal. Renewed
vows have no true effect on a marriage, but still some people like to
have the reminder.