Conform dicționarului Oxford, forma ”thousands” se folosește numai atunci când înainte de aceasta nu există indicații de număr sau cantitate.
You say a, one, two, etc. thousand without a final ‘s’ on ‘thousand’. Thousands (of…) can be used if there is no number or quantity before it. Always use a plural verb with thousand orthousands, except when an amount of money is mentioned Four thousand (people) are expected to attend. Two thousand (pounds) was withdrawn from the account.