ZDC Controller described an airspace incursion noting concern regarding the facility's policy of increasing sectors in each area; the training process and the lack of currency time afforded on the new sectors.

Narrative

[I] worked 2 very; very busy and long sessions prior. Once with D-Side and 2nd time no D-Side but with FLM not certified at sector plugged in to assist. Just combined Sector 36 and Sector 16 together and previously was descending all BWI arrivals to FL270 for volume. My normal sectors descend all BWI to FL270 as standard procedure. Just went and gave a B717; a BWI arrival; my normal clearance even though I was not working my normal sectors. Due to this ZDC 8 areas to 6 areas change; I am now certified in 10 sectors and training on 11th sector. I was working overtime outside of my normal area to assist area 2 with their overtime. Sectors 16 and 36 are not my normal sectors and it had been several weeks since I had worked them after the accelerated certification. After the intense first 2 sessions; this third session I must have relaxed and gave standard descent to FL270 when I should have descended to FL280. ZDC be more safety oriented verse goal oriented of changing from 8 to 6 areas. Controllers are pressured to check out quickly to keep process moving. Training hours have been reduced. Once controllers are checked out; there is no plan for currency. Every 30 days when FLM's think of it sometimes Controllers are sent to recently checked out sectors for currency. Whether for 1 min or 1 hour and whether there is no traffic or not the box for currency is checked. My currency has already expired in one sector; a high volume and complex sector; which is a brand new sector for me. I expect to be thrown in there when it is busy as I was previous sectors.