For how long you can leave the 6month old baby go sit ?

Let them be: Some 6 mo can be propped in sitting and may stay upright until they tip over.Most will only stay up for a few moments.Those with the ability to stay longer can be left alone.You need not worry it hurts their spine if they sit for long periods.By 10 months most get to sitting and stay up until they decide to do something different.

Not long: If you mean sit without support, depends on the baby's level of muscular stability, but probably a few minutes at a time if he/she has just begun to sit up without support. Make sure this is done on a soft surface so they don't bang the head badly when falling over to the side or backwards, you really should try to prevent them from falling over without you breaking the fall with your hands