If i travel to Thailand without a visa and get the 30 day extension while im out there - how soon would i have to do this prior to arriving. Thanks

Common sense suggest that it will be same as any visa obtained from an embassy/consular office in person or by mail. There is no difference in visa if obtained through the e-visa portal or from a embassy/consular office in person or by mail. 

There is no extension of a visa. It's the permission to  stay that is extended inside Thailand at an immigration office. There is no concept of extension of a visa outside or inside Thailand. However, colloquially an extension of permission of stay inside Thailand is generally referred to as an extension of visa. 

You’ve posted in the forum for visas to countries other than Thailand, I’ll move your question to the appropriate forum.