Wall Street firms will often have 12 month noncompetes but you get paid for that year. Details matter however. Like you might be paying for health insurance (COBRA). You won't be getting any bonus. Any bonus money in the fund gets removed and put into treasuries, which in some years may have a better performance so that's a mixed bag.
If Wall Street wants noncompetes, the employee should get paid 1.5 times the annual average total compensation they had for the previous 2, 3, 4 or 5 years, whichever is best for the employee.
Wouldn't everyone quit after having two unusually good years back to back?
I see this as an "all or nothing" type thing. When the employee quits, the company decides to enforce or not. If they enforce, they're on the hook for the entire noncompete period. No deciding after a month not to continue enforcement.