Concerning tithes, do we owe tithes for the years we didn't attend any church?

Tithes were for Israel and NOT today's members of the Body of Christ or professing Christians, and they were never paid in cash, but were to feed those in need. NOTHING to do with our day and anyone telling you different, especially the Church, is lying to you so as to profit from misinterpreting the bible.
Eze 44:30 (NIV) The best of all the first-fruits and of all your special gifts will belong to the priests. You are to give them the first portion of your ground meal so that a blessing may rest on your household.

Eze 44:29 (NIV) They will eat the grain offerings, the sin offerings and the guilt offerings; and everything in Israel devoted to the Lord will belong to them.

Thus, there were offerings of animals, grain, and wine, of which the priests also received parts of. Besides that, the priests also received ten percent of the Israelites third year's tithe, portioned out by the Levites.

Deu 14:28,29 (NIV) "At the end of every three years, bring all the tithes of that year’s produce and store it in your towns, so that the Levites (who have no allotment or inheritance of their own) and the foreigners, the fatherless and the widows who live in your towns may come and eat and be satisfied, and so that the Lord your God may bless you in all the work of your hands".

Deu 26:12 (NIV) When thou hast made an end of tithing all the tithes of thine increase the third year, which is the year of tithing, and hast given it unto the Levite, the stranger, the fatherless, and the widow, that they may eat within thy gates, and be filled;

Num 18:25-28 (NIV) The Lord said to Moses, “Speak to the Levites and say to them: ‘When you receive from the Israelites the tithe I give you as your inheritance, you must present a tenth of that tithe as the Lord’s offering. Your offering will be reckoned to you as grain from the threshing floor or juice from the winepress. In this way you also will present an offering to the Lord from all the tithes you receive from the Israelites. From these tithes you must give the Lord’s portion to Aaron the priest.