I've noticed that on the items I bid on,someone comes around in the final hours and jacks the bid up. I've learned to not counter bid. Instead I use my bidder app I got off iTunes App Store and set my final bid and lay low in the bushes. If I really want it I'll set my bidder at a fairly high price and if I win the bid,I buy it for my disclosed bid on Ebay instead of on my bidder unless other bidders went higher. Some bidders will try and snatch it away up to a certain price and then stop like if the're buying it to resale themselves. If it's a very collectable item some will fight you for it.
P.S. Sometimes I'll jack my Ebay disclosed bid just above the other bidder and if they outbid me I just lay low and act like I'm not willing to outbid them.