NHS waiting times have lengthened so much that it could take many years to get them back on target in England, experts say.
There are three flagship NHS waiting time targets covering cancer, A&E and routine operations.
It is more than three years since any of them were hit in England.
And despite the pledges of extra money for the NHS by the three main political parties, it could take until well into the 2020s for progress to be made.
One of the big problems is lack of staff. There are nearly 100,000 vacancies in England, about one in 12 of all posts in the workforce.
It takes five years study to become a doctor and three years to become a nurse.
Prof John Appleby, of the Nuffield Trust think-tank, said: "It is not just about money, you need the staff and equipment to see and treat people.
"Then you have to factor in all the competing priorities, such as mental health.
"It could be another year or two before we even start to see waiting times improve. To get back to close to the targets could take four years at least.
"The NHS has had to get by on less money than it is used to for the last decade. The impact of that cannot be reversed quickly."
The British Medical Association said it could take until the end of the next decade to get back to hitting the targets routinely.
BMA leader Dr Chaand Nagpaul said: "The NHS has been significantly under-funded for more than 10 years. The situation cannot be clawed back overnight."
Scotland, Wales and Northern Ireland are all struggling to hit their targets, although health is devolved so NHS decisions are taken by the administrations in those parts of the UK.
'I was left in excruciating pain'
Frances Reid, 55, said she was left in "excruciating" pain waiting for her hip replacement.
She was referred for surgery in January 2018 after struggling for the previous two years with hip pain.
She should have been seen in April 2018, but waited until July for her surgery.
The NHS ended up paying for her to be treated at a private unit because of the wait.
"The final weeks were really difficult. I was waking up six, seven times a night and had to use walking sticks to get around.
"Daily tasks like shopping became very difficult."
Prof Derek Alderson, of the Royal College of Surgeons of England, said the impact on people like Frances could be "devastating".
He said: "Latest figures show more than 650,000 people across the country have been waiting more than 18 weeks for their operation. In those months, their physical condition can deteriorate, they can become depressed, suffer in pain or lose their jobs."
In a joint letter with the charity Versus Arthritis to party leaders, the RCS has urged ministers to keep the 18-week target for routine treatment. NHS England is exploring new ways of measuring performance for that target and also the A&E one.