I have a DD now age 10 and a DS age 2. For us, the age gap has worked out perfectly - DD has benefited from all our attention for so long, she has always wanted a sibling so she was overjoyed to get a baby brother and so far the novelty hasn’t worn off.
As she is older she spends a lot more time doing her own thing, and she has almost never been jealous of the attention the baby has had. She loves playing with the toddler and I have been careful not to make her responsible for looking after him, except for the occasional “I’m just popping to the loo, keep an eye out for DS doing something silly while I’m out of sight.”
I have no illusion that when she is a grumpy teenager /independent young woman, she will be less interested. And when she flies the nest, we will still have her little brother and he might miss her company. But with any family, there are challenges having teenagers in the house, and I expect my son will have a full and busy life himself so I really don’t anticipate major problems. I could just as easily have two kids close together in age who don’t get along, or who compete for attention.
I absolutely enjoy having children in my life, and so does my DP so the idea of having two “consecutive” kids to deal with has never phased me. I truly do not view them as single children, they have a close bond that is nothing like my DD with her cousins, and nothing like a parents’ bond with a child. Of course it isn’t like having two little kids who are tumbling around and learning together, but life didn’t give me the option of two kids of a similar age. I am very, very content with my family and wouldn’t change it for the world.