Yes, I've used L'oreal casting colour creme for about 10yrs. Its a semi, so washes out after 24washers apparently. I never leave it that long before colouring again though. I'm a similar age, and would likely be 50% grey I'd guess. As a child I was naturally a milk chocolate brown. I did have a few permanent colours in my 20's, but didn't like the permanent re growth line.
Why- I've had some dreadful results at a hair salon! Twice, 2 different salons and different countries I had some highlights put in- they were awful. 1st time they put highlights and low lights in. My hair was already dark so the low lights were invisible, and my hair looked like massive zebra stripes. The hairdresser said they'd settle and blend in- they didn't!
Another time, when the foils were removed- so was my hair! When they put the colour on the rest, instead of a chestnut brown, it was a mulberry purple. I spent months with tiny, spiky bits of hair sticky out where they'd all broken off. The hairdresser said it was due to me having some greys! I work full time and can't stand spending half a Saturday sitting in a salon, making idle chit chat, waiting for my hair to be done. Along with covid, I've just coloured my own hair for years.
The brand I use comes out darker than you'd think, so I always go several shades lighter. I buy light brown or chocolate caramel- which gives a slightly chestnut colour. I'm sure I will need to go to a permanent colour soon or back to a salon, but for the moment, I'm happy doing my own every 6 weeks of so- for a fraction of the cost and about 1/5 of the time sitting in a salon.