Great question!!
With my older three, I had studio photos done every 6 months to a year. Sears, Walmart, etc. They were ok, and many are still on my walls in my upstairs. Once my kids entered school, I just paid for an 8x10 of a school photo that I put in a very thin-frame and hung on my wall leading upstairs. I like it because you see the maturity and growth all in one place.
I had a toddler come along later...and I have yet to get her pictures taken!! She is amost 2!! In the last few months, I've had several people tell me (not in these words) that I'm a bad mom because I haven't had her pictures taken. I was going to get some taken next month, but have changed my mind.
My best friend who lives in Georgia, is the best photographer I have ever seen. She has a gift, for sure. She came to visit two summers ago and took pictures of my kids here at our house. My toddler was 6 months at the time, and those pictures are more precious to me than anything. They weren't staged or studio. They were my 7 yr old daughter climbing a tree or my baby sitting in a basket with our pond in the background. I had an antique highchair that she put the baby in, which had our barn in the background. Beautiful. Our nighbor has some old farm equipment (wagons, corn sorter-type things) that are old and rusty. To us, they are kind of eye sores, but to my friend, they were the perfect backdrop to my two cowboy boot-clad sons! She captured their quirky smiles, them trying not to laugh and even a little tussle in the grass. I cannot even tell you how much better those pictures are than any of the studio-sit-down-and-pray-they-don't-bawl sessions. It was very relaxed, no tears. It was them doing what they normally do, but with very nice clarity and editing. (She made our white pony almost animated, she was so pretty and bright). I could go on and on - oops, I have! :) I will wait to see if I can get my friend to visit again this summer. I would pay for her plane fare, just to get her here to take more. LOVED them!!! I do not want to try to get small kids to sit and smile for the camera ever again.
If you have an eye for photography, I say experiment. Sit and watch your kids play and try to capture a couple candid moments. I truly think those are more precious than any staged photos. If you can get some really good ones, yay!! But, if you want to find someone to come out to your house and take some at your house, or your favorite park, pretty stream, grandparents farm, etc. I would say it would be worth it. Like I said, my friend will do the photos for free, but I would not hesitate to pay for her to fly to Ohio to take more. Many phtotographers are doing the "lifestyle" shoots. They go to where you want them. Search around to see what's offered around where you live. My friend is now concentrating on those types of sessions instead of any studio shots.
Good luck and have fun!!