Before recharging I rest a discharged battery until it comes to room / ambient temp + 15 minutes.
Sometimes that equates to 15 minutes other times like when being used outside during the summer that may take 2.5 hours.
Resting a freshly charged battery is always a good idea.
Like explained in the previous post above the chemical exchange that takes place during charging is rather aggressive / violent, it takes time for it to settle down & stabilize.
How long depends on several factors, using a good quality 'soft start' & slow / trickle finish charger helps reduce resting period.
A good rule of thumb is an hour or two, but, a crappy charger or high temps = longer rest period.
The benefit to resting is increased battery lifespan & minimize chance of venting.
The better you treat your batteries the better they treat you.
BTW, you may want to buy a few 'better' batteries.
The cost of using so so batteries is more than the price of good ones.