Stroke patients should be offered extra rehabilitation on the NHS, say updated guidelines for England and Wales.
The National Institute for Health and Care Excellence (NICE) had previously recommended 45 minutes a day.
But it believes some patients may need more intensive therapy for recovery and is suggesting three hours a day, five days a week.
Experts welcome the advice, but question how feasible it will be for a stretched health service to deliver.
NICE accepts it may be "challenging", but it says patients and families deserve the best care possible. That includes help regaining speech, movement and other functions caused by the damage that happens to the brain during a stroke.
NHS England has said increasing the availability of high quality rehabilitation is a priority. More people than ever are surviving a stroke thanks to improvements in NHS care, it added.
A stroke cuts off blood supply to parts of the brain, killing some cells. They are common and can affect people of all ages, but many patients survive if they receive prompt treatment.
All strokes are different, depending on the part of the brain that is damaged. For some people, the effects may be relatively minor and may not last long, while others may be left with more serious long-term problems.
There are around 85,000 strokes every year in England, and around a million stroke survivors, many of whom are living with long-term effects.
Some of the injury is reversible, though, with help from health teams providing services such as physiotherapy, as well as occupational, speech and language therapies.
Although strokes usually affect older people, about 400 UK children have a stroke each year in the UK, leaving many with severe physical and mental after effects.
Brenna Collie, who is 21 and from Aberdeenshire, had a stroke in 2017, at the age of 14.
Brenna, who was a very sporty teenager, had intensive physiotherapy for about a year so that she could learn to walk again.
She's since been able to return to archery and playing hockey. During the Covid pandemic, Brenna learnt how to knit with her affected arm.
But she still experiences some after effects of her stroke - she wears an ankle support to help with a weakness called drop foot.
"I still have left sided weakness. I have neuropathic pain down my left side and I have migraines, light sensitivity and fatigue."
NICE says the evidence it reviewed when updating its guidance showed more intensive rehabilitation improves quality of life and important daily skills, such as being able to dress and feed yourself.
It also heard from people recovering from strokes, and from their families and carers, who felt strongly that more intensive rehabilitation would be useful in helping them recover faster.
Prof Jonathan Benger, chief medical officer at NICE, said: "We recognise the challenges the system faces in delivering these recommendations, not least the problems inherent in increasing service capacity and staff. We also know current practice is inconsistent, even when it comes to implementing our previous recommendations.
"But equally, it shouldn't be underestimated how important it is for people who have been left with disabilities following a stroke to be given the opportunity to benefit from the intensity and duration of rehabilitation therapies outlined in this updated guideline."
Dr Maeva May from the Stroke Association said many stroke survivors receive only a fraction of what the guideline recommends, partly because there are too few staff to provide the care.
"It's vital that governments act urgently to address staffing issues across health and social care, and within rehabilitation services, and share detailed plans to support and resource them, so that these recommendations can become a reality," she told the OceanNewsUK.
An NHS England spokesperson said: "Despite the current workforce and capacity pressures acknowledged by NICE, the NHS is delivering high-quality specialist support for stroke patients - including through physiotherapy, occupational therapy and speech and language therapy - closer to patients' home."
If you suspect that you or someone else are having a stroke, call emergency services - 999 in the UK - immediately and ask for an ambulance.
The main symptoms of stroke can be remembered with the word FAST:
