hello
@Wilsoner
and welcome to DTP
you don't give much detail on your parents' circumstances, and you say up to 3 hours, so that could be some minutes in the car while your mother pops in to a local shop
sounds to me as though this has so far worked for your mother, she will be weighing up the risks and know how your father copes when on his own
I wonder what options your mother has ... maybe she doesn't know what support there may be available to her
perhaps you can help her by suggesting online grocery shopping ... can you or someone visit with your father while she has an hour or so to get out by herself
if there hasn't already been an assessment of your father's care needs, let your mother know about this and that he has a right to an assessment and she has a right to a carer's assessment ... might you contact their Local Authority Adult Services for them to make arrangements ... from the assessment a care package may be suggested eg some home care visits, time at a day centre so your father is looked after and your mother has time for herself, a befriender to visit to be company for your father while your mother has a break, and respite
there are some helpful pages on the AS site
https://www.alzheimers.org.uk/get-support