Tenant disputing Sec. Deposit charges - time limit they can?

[Edward R.]

My property is a fully furnished house; I do short term rentals only in NYS. 

  I had 3 guys in there for a 2 month lease in late October (company paid for). 18 days into their lease I discovered pot and smoking going on in the house and on property.  They admitted to it and after another inspection I gave them an option to stay with lease modifications.  They blew me off for a few days. Then offered them key-for-cash to get out in 24 hours;  it was 10 days of rent.  They agreed and signed a lease cancellation agreement.  They weren't there for inspection despite them knowing.  Found a few buds in a dresser drawer.  

Anyways.  I kept the full deposit charged for the environmental cleaning and stanley steemer.  Sent them the certified notice and details of the charges and discovery of smoking crap.  26 days later I get an email from one of them; 

"sorry for the delay.  We just saw the charges and we don't agree. felt they were aggregious.... We'd like to discuss a fair cost and leave this agreement in peace" 

It was something like that.  Seriously, they signed a smoking addendum in the original lease, company agent did too.  They fraudulently entered into a contract knowing they would break it.  leave pot around.  could easily smell it despite them saying they only smoked on patio.  I don't care about people smoking pot and such, just not in my property.  (hell they can grow their own pot garden at home for all I care)

So my question;  26 DAYS?  does NYS have a a rule (or yours) about time limit a tenant can dispute deposit charges?  I followed my time limits.  What have you done in this situation?   I have no intention of coming to an "agreement"  they are the ones who screwed up and cost me time and money.