The advantage to using ebay labels in your situation would be that regardless of if the post office is open or not, you can still generate a shipping label and tracking for any sale at any time.
What you're doing now is probably fine for now, but if you plan to expand later you may want to consider some changes.
1. I can not recommend enough a thermal label printer. It doesn't use ink and you can get free labels. A thermal printer has made shipping for me so much better. Especially for my lighter weight items, ever ounce counts when you're shipping first class and the labels weigh nothing, so they won't contribute to the weight of the package. You shouldn't have a problem finding one on eBay.
2. Postage scale. You can find a 10 or 25 LB scale pretty cheap on eBay. This gives you the advantage of paying for exactly what you need instead of guessing the weight.
3. Ebay labels gives you a pretty significant discount that you won't get at the post office.
You can find a list of thermal printers here, these will work with paypal as well.
http://pages.ebay.com/sellerinformation/shipping/PPshippinglabelsfaq.html
I use a Zebra LP2844. If you get one i'd suggest going with a LP version (direct thermal) TLP uses transfer film.
4. You can get free labels from UPS and Fedex. Just create a Fedex and UPS account. Under shipping supplies you can order labels for your printer and get them sent to you for free.
- Fedex will track your usage, so unelss you ship with Fedex you wont' be able to re-order without them giving you a hard time.
- UPS allows you to re-order every 3 months regardless of your usage.
That's probably more info than you needed but it's something to think about.
