Best way to keep dark lashes?

[potentialzaddy]

I currently get my eyelashes tinted with my hair dyed dark every 2 months but I was wondering if there's a better way to maintain or keep my lashes dark? They're blonde but I have a lot of them so it makes quite a big difference, it fades towards the second month but I feel like booking a lash tint in is kinda pointless every 4 weeks