I'd offer it as an add on.
I've only had it a couple of week's, so am no expert in using it.
Not every head will need it. In fact, so far, I'm quite proud to say most of my client's don't NEED it.
Over the year's, I've got them into a regular 4 - 6 week routine, to include home care.
That's not to say the odd 'Scary Mary home bleach' doesn't enter the salon....it's on these occasion's I'd reach for the OLAPLEX to save the day!
Client's with poor porosity could benefit from adding to the mix, but as has been mentioned, not sure how the different colour houses will feel about this addition to their product!
If using as a treatment, make sure you take into account the extra 20 mins it takes, and not just charge for the cost of the product.