Customizing OM Negotiation Header (OENH) workfow not working...

Hello
I am in R11.5.10.2 version and I have requirement to get the pre-expiration notification before 10 days of quote expire, to do this i have updated an attribute "PRE_EXPIRE_TIME_PERCENT"  from 10 to 100 to get the pre-expire notification before 10 days of quote expiration instead of 1 day. After i updated the attribute i have created a quote which will expires in 4 days and ran the workflow background process, but I have not got any pre-expire notification. Is anybody worked in such a requirements, plz suggest is I am missing anything?

Setting the Offer Expiration Date

You can limit the validity of the Quote to a specific period and assign an offer expiration date. The workflow updates status at expiration, and expired transactions may be purged. This date can be manually entered, or defaulted. For example, if you use defaulting rules and select a defaulting condition for negotiation, then select the system variable and enter sysdate+1, the expiration date will default 1 day from the current system date. Notifications can be generated prior to expiration. The expiration date ranges can be used in a search.