How often do you chat to your grown up children?

My eldest child has ASD so weeks can go by without any communication from them. They live with their partner (also ASD) in the same town as me but neither cope with me dropping in unannouced, and both struggle with telephone communication, so I send an e-mail most weeks but often don't get one in reply. Eldest posts regularly on other social media so I tend to check there to make sure they are still ok.
Youngest lives about an hour's drive away and has a very demanding job so again e-mail (sometimes every other day, sometimes less frequently) is our preferred method of communication, but we do manage to see each other a couple of times a month usually.
Not sure how normal this is - my sister-in-law speaks to both of her adult children daily on the phone and they drop in to each other's houses several times a week it seems. I do sometimes wonder what they find to talk about but it works for them - just as my way works for me and mine. I do know that if I need to I can call on youngest who will drop everything to come and help me - not so much eldest but that's because of their issues but they would do their best too.
As you say, many of us lead busy lives these days and sometimes it is difficult to co-ordinate a time for telephone chats or meet ups. I think it's pretty useless to compare yourself to others as you never know the real story. One of my youngest's friends has a mother who seems to want to be involved in all aspects of her life and she hates it but goes along with a lot of it as her mother is always telling her how lonely she is.

I get little texts or messages from my mum once a week or so. I see her twice a year and can't really spend more than 2 days with her without getting annoyed. We have never been close and there are things I can't forgive. I know my mum realises this and is trying hard to make up for it but I'm afraid cocktails and pamper days don't cut it as I needed her most when I was a child. I do try to make effort as I feel sorry for her but every time I do I end up regretting it.

I live at the other end of the country. One brother lives at home and my eldest brother sees her often as they live nearby and she helps look after his children. I would love my mother to be involved with any future children as I do know she's a great grandma and it would bring us together (if she didn't get too interfering). I know it's never too late for us but I did move away to start my own new life without the past. I've always been the sort of outcast of my family but I prefer it this way.

If I have children I imagine me giving them little texts every day and missing them all the time and wanting that mother-daughter bond I didn't have with my mom. Like going on holidays together, her telling me her boyfriend problems or whatever.

I don't think you're a terrible mum and it goes two-ways if you want to remain in contact. If you're really worried, can you ask your children how much they contact they feel they need? I try to tell my mum I need space as she can try encroach on my life and not respect my space and that I'm an adult.

Text every day and sometimes throughout the day. One in UK one in China. Both boys (men!). It's a great way to just check in with them. Usually just stupid stuff. I'm not so good at keeping in touch with my parents though, phone once a week.