I have a 13 month age gap. The youngest one is 3 months and I feel like things are starting to get a little easier now. Having spent lots of time thinking about this when I was pregnant, I came to the conclusion that any age gap comes with it's good and bad points.
I'm 99% certain we're stopping at 2, so I'm glad that we don't have to go through TTC again and the worries about whether or not it will happen (first time took a while, second obviously didn't!), won't have to be pregnant again (loved it first time, found it much harder second time), don't have to give birth again, will get the sleepless nights and nappy stages out of the way etc. I feel like we can start to focus on other things too (hoping to move house in the next year or so) and enjoy seeing our kids grow and develop.
You don't have things like school runs to contend with if you have a small age gap. My friend who has just had a baby also has a preschooler and a primary school age child and she is juggling school runs with different pick up times every day, getting kids up and out for school, and also dealing with a newborn baby who might have been up during the night. That sounds much more tiring than my situation.
It is hard though as it's constant. The older one is still too young to be sensible, so I'm often trying to feed the baby and stop the toddler falling off the sofa or trying to poke the baby in the eye. I felt guilty about the effect on the older one at the start, but I don't really feel that any more. I'm spending more time with her as I'm on mat leave (if I was working I'd not see her during the day) and she's starting to enjoy her sibling which is lovely to see.
I do have good family support and I think I'd find it really tough if I didn't have that. I can drop one off with a family member for an hour or two and take the other one to a class or something. The older one still goes to childcare 1 or 2 days a week which is great, means I can get housework done, go meet a friend for a coffee and actually get a chance to chat, or just take the opportunity to sleep when baby is napping if I need a rest.
It is tough to start with, but not in the same way that I felt so overwhelmed with my first. I feel much more relaxed this time, it's just tiring running after a toddler while looking after a baby too, especially if you've not had much sleep or one of them is sick.
But I'd say it's definitely worth it, you're definitely not mad to be considering it!