So I use it 4-5 days a week. I always use it when on holiday/during summer to protect the smp from the sun.
The main things that will fade smp are most likely: UV from the sun & also your immune system, whilst ingredients of creams, shower gels etc may contribute to fading they won't have a huge impact on smp. Not much we can do about our immune system response so the only one left to worry about is sunlight therefore sun cream is a must, and vichy just happens to have an amazing matte effect as well as sun protection.
I've had smp for over 5 years now, had my 1st top up session last year, I've tried many creams for matte effect and for years now I've been using Vichy as it is in my opinion the best by some distance. At night after washing off the Vichy I apply either argan oil or jojoba oil to my scalp to keep it in good condition, I also prefer a good foil shaver such as a Braun/Panasonic because for me they cause zero irritation and help keep my head looking its best. Everyone has different opinions on razors, creams etc but for me this is what works after years of trying various approaches for maintaining smp and keep it looking its best.
A typical day for me:
Morning - shave with Braun series 7, apply Vichy if I want it on that day.
Night - wash and then apply 10 drops of argan/jojoba oil to scalp to keep it in top condition (the oil also makes shaving the next morning even quicker)
That's what works for me it's quick, no shine, no cuts or irritation etc
The cost of all this per month I'd say is roughly £22 based on.....
Every 2 months I replace the foil/cutter on my Braun shaver @ £25, so per month £12.50
Every month I use just under a bottle of Vichy so per month £7
Every month I use a quarter bottle of argan/jojoba oil so per month that's about £2.50
Hope that helps.