Hair History... What next?

As you can probably tell from the picture above I have had almost every type of hair colour going. From natural brown, to red, purple, ombre and most recently blonde. I started going blonde slowly about two years ago and as you can see from the pictures, was very blonde for about a year. I loved it, my hair did not! About 6 months ago my frazzled hair couldn't take it any more and I realised I was going to have to give it a break for a while before I ended up having to wear a wig for life!
I asked my hairdresser for the best option and she suggested semi permanent brown all pained over my roots and blended leaving some of the bleach at the bottom. Due to it being semi permanent it slowly faded and I now have very noticeable blonde ends to my hair, a natural dip dye if you will.

This picture is the most recent one I have of my hair, and although I love how healthy it is, and how much it is growing, there is a little voice in my head making me want a change. Looking back at all these pictures is really tempting me to book an appointment and go back to blonde, but I just don't know if I can commit. 

This is where I would love your input and advice. Any blondies gone to the dark side? What's the best way of going back ? Is it worth the money and upkeep? All this and any other pearls of wisdom would be great.