Help! Does bleached hair need colour care products??

If it is depositing color (which it sounds like it is, because lightening the hair will reveal very warm, not ashy tones) then I think Color Care products could help you, really it's all about ingredients though. A lot of 'Color Care' shampoos have sulphates in them which are terrible for hair color. So I would say if you're looking to extend your color more, use a sulphate free shampoo. If your conditioner has silicones in it (most do), just be sure to use a sulphate based shampoo every couple/few times you wash so you don't get buildup. You can do a vinegar rinse after dying too - just dilute some regular white vinegar with water 50/50 and spray/pour it over your hair after you've washed + conditioned. It helps close the cuticle and keep color in.

Another thing you can do too to help keep it cool toned is buy a violet semi, like Manic panic Ultra Violet, Directions Violet, Pravana Violet, etc, and add some to your shampoo and conditioner. You can even use your conditioner as more of a toner by putting it on your clarified, non conditioned, product free hair, and letting it set longer. You can add more dye if you need to to tone it more. Semis are completely non damaging so you can use them as many times as you want and never suffer any damage from them, they're like highly pigmented conditioners. If you want to add even more ashy/silver tones to it, dilute some Pravana Silver in a bowl of conditioner and apply it the same way

Are you using the Max Blonde on the entirety of your lengths/ends every time you dye? Or just doing the top part of the dip dye as your hair grows?

Some other good products to have for lightened hair are Joico Kpak Deep Penetrating Reconstructor, Aphogee 2 in 1, or even doing a mayonnaise mask once a month or so to help add some protein back into the hair, which gets damaged when you lighten it. Another really good thing to have is some coconut oil. You slather it on your hair at least a couple hours before you lighten it, then just apply the dye/bleach right over it. It really helps keep the damage down
http://www.hairdyeforum.com/index.php?topic=3806.0
It acts as a great moisturizer too as it is one of the only 2 oils capable of being fully absorbed into the hair, along with argan oil. A lot of people do overnight coconut oil soaks, then in the morning coat your ahir with conditioner, let it set for a half hour or more, then rinse it out in warm water.

This is a great product too:
http://www.hairdyeforum.com/index.php?topic=12305.0

Wow thanks for your reply that's super helpful!
I wasn't sure if it was adding colour or stripping it away hence the confusion about the necessity for the colour care products. When I dip dye it I concentrate it on the very ends and slowly build it up to about the mid-lengths. I don't really top it up which makes it low-maintenance, but when I get my hair cut I redye it then.

I had better start investing in these sulphate free shampoos, do you mean SLS when you say sulphates? In which case my current treseme routine does include SLS  😮

I do use the purple toner shampoos when I feel my hair's looking a bit dull and brassy, I used coconut oil before dying it but I read somewhere that using coconut oil AFTER dying is actually bad for the colour! Not sure if it's true or not though it's so hard to tell with all this information floating around on the internet sometimes.
Thanks again for all the info and tips! I'm deffo looking into these different products