 Re: "to last for a month" or "to last a month"
Both are fine. It's quite usual to drop the "for" when you're talking about a period of time and the verb itself expresses duration - eg : I've lived here for about a year or I've lived here about a year. It's only when the verb doesn't express duration that you need to make it explicit by using the pronoun. So : We stayed for half an hour or We stayed half an hour are both fine but only We went for half an hour. Because in fact it's not the act of "going" which lasted half an hour (and there's your example - last expresses duration so for is optional). The sentence implies "We went and then we stayed".
Hope that helps. |