hours needed per clean - 2 2.5 3 3.5 etc
how often - weekly fortnightly monthly
and duration - 1 moth -6months

Should just be a matter of 2 fields and 6 plans to provide that. Your 2 fields would be for selecting frequency and number of hours. Your plans would be for the duration.

my question is if I use cb subs and client chooses 2hr clean weekly for 2 months will i be able to get it to add this up automatically and they go through checkout?

Yes, CBSubs Promotions allows dynamically increasing the price of a plan via negative promotion (e.g. -20 increases the price by $20 instead of decreasing it). Using this you could have a promotion per frequency available and hours per cleaning available to increase the price.

I'd probably create 6 plans with duration's of 1 month to 6 months. Then have 2 fields to specify hours per clean and how often. The plans themselves would have a base price based off duration (e.g. lets say $10/mo with a minor discount for purchasing multiple months). Next I'd setup that negative promotion to adjust the price based off hours per cleaning and frequency. You should be able to give this all a try on our demo site below to see if CBSubs would fit your needs.

demo.cbdemosites.com/

Lets for example say I've the following plan structure to handle duration.

Plan 1 - 1mo, $10, exclusive
Plan 2 - 2mo, $20, exclusive
Plan 3 - 3mo, $30, exclusive
Plan 4 - 4mo, $40, exclusive
Plan 5 - 5mo, $50, exclusive
Plan 6 - 6mo, $60, exclusive

Next I'd have 2 select fields. Something like the following.

Frequency
Option 1
Value: FREQUENCY_WEEK
Label: Weekly

Option 2
Value: FREQUENCY_FORTNIGHT
Label: Fortnightly

Option 3
Value: FREQUENCY_MONTH
Label: Monthly

Hours
Option 1
Value: HOURS_01
Label: 1

Option 2
Value: HOURS_02
Label: 2

Option 3
Value: HOURS_03
Label: 3

Now you'd just need 6 negative promotion plans 1 for each Frequency and 1 for each Hours option. You can condition based off the field value using the parameters under the Condition tab while editing your promotion. How much these cost would be up to you of course.