I'm a bit higher than average for freelance hourly. I'm thinking about getting more into "charging by value" (as opposed to hourly) because I get a lot of resi

I'm a bit higher than average for freelance hourly. I'm thinking about getting more into "charging by value" (as opposed to hourly) because I get a lot of resistance to raising my rate even as I get faster - but I'm not really certain how to do this since I tend to have long-term relationships with my clients and my work generally doesn't tend to have clear start/finish boundaries. Curious to hear if anyone has figured out a way around that.