5 months - is it OK for her to sit for a lot of the day?

DD, 5 months, has been able to balance sitting, with increasing sturdiness, for about a month now. She can't sit herself up, but when placed she can stay balanced, Now she can sit for 30 minutes or maybe longer without toppling over. I put cushions around her, but she isn't leaning on them, they are just there to save her bumping her head if she goes down

Is it OK for her to spend hours every day sitting on the floor playing with her toys? I think she's been there 2-3 hours in total today. I've been around, doing housework and the dreaded tax return...

She seems to enjoy it, but when I think about it, it's an awfully long time to sit, for someone who has only just learned to do it.

What do you think?

Mmmm, if she is happy playing I couldnt see why not. If you are concerned though you could always pop her on her tummy for a bit and then go back to sitting once she bores of it? Or just alternate between back, tummy then sitting??

Both of mine were sitting for most of the day by 5 months and one of them was starting to walk around furniture by 6 months (according to my plunket book I did the same thing at that age, too) and they are both fine at 4.5 and 8 now - never had any back/leg problems etc. I would be inclined to let her go if that's what she wants to do? ;)