There are all sorts of ways in which you could support them and some people might feel comfortable with some tasks and some with other tasks. These might include finding out about benefits (eg attendance allowance), help filling in forms, navigating the 'modern world' e.g tech, websites, finances & smartphones, discussing health worries, finding a gardener / cleaner or doing domestic & DIY tasks.
Speaking from vast experience here, each and any of the tasks listed above can take an inordinate amount of time, depending on the prent involved, their physical and mental state and their current and future ability to navigate IT and the care system. Ditto 'the occasional trip to the chiropodist' mentioned in previous posts.
For me it was something of a slippery slope. What started as sometimes taking a parent to the supermarket, escalated rapidly to me being the one who was called upon for everything. I hated it every time the phone rang because it would be another request demand for help, or a plea because the TV/phone/microwave/whatever 'isn't working anymore'. And when social services or specialist care made suggestions or offered the kind of help my parent should have had, it was met with "No thanks, ModernDilemma will do it. We prefer it that way."
Honestly, there was a year when I wept every day with frustration. It was only when my 91 year old father went into hospital that the issue was forced.
PILs went on a similar journey with dp and his siblings. What started as one organising cleaning help then a carer, became a nightmare when MIL would sack them fortnightly, stating that she didn't need any help.
And despite best laid plans things can take their own course. dp was on a visit to MIL when she fell. Paramedic assessment said she didn't need to go to hospital and dp was thrust into being the de-facto carer for his parents (both of them since neither could operate independently). That included all domestic tasks, all admin, and personal care.
PIL live 2 hours away so dp moved in for a week. Which turned into 3 months (with some respite from his siblings when they weren't at work). Because someone was in the house social services didn't deem PIL to be at immediate risk and they were very low priority against all the other priorities.
When my time comes (or actually well before it) I plan to pay for a network of support - a PA to help with life admin; a tech person to help with whatever technology is around; cleaner/housekeeper to change the sheets, help with cleaning, help with shopping; a companion to take me on trips in the car. All of them just a couple of hours a week. I would rather use my money on that, and then on whatever residential care that I might need, than be a burden to my dc during my life. I'd prefer that my dc fulfill the role of family, keeping me involved in social activities rather than being at my beck and call.