You're a little off in your assumptions... here's how furniture buffs work. While you're in your house, whether online or logged out in it, you accrue a given number of rested xp/tp per hour. These numbers are increased or decreased by the furniture in your home. If you have a table worth +25 TP, and a lamp that gives you +10, every hour you're in your house, you'll receive +35 rested TP. These numbers will accumulate on your xp bar at the bottom of your screen, above your main action bar (default settings), which can be checked by mousing your cursor over it. There will also be 2 arrow indicators on your bar, that give an indication of how much additional xp or tp you'll gain in relation to your current experience bar.
There are level caps to how much maximum rested xp/tp you can gain. A player of a higher level can store more rested xp/tp than one of a lower level, this is because the pool for how much xp is required to level increases for each level you've already reached.
The way to SPEND those rested xp/tp points, is done by killing monsters. Every time you kill a monster, it yields a given number of xp/tp dependent on the mob type & level in relation to your own. For example, a monster of a higher level than you, will give more xp/tp than a monster of a lower level than you. Additionally, more difficult monsters such as elites will yield even more xp/tp per kill. Now, when you have rested xp/tp, when you kill those monsters, you will receive an additional 50% of the xp/tp the monster would normally yield. For example, if a mob normally gives 100xp/10tp; when you have the furniture bonus, you will receive 150xp/15tp. This bonus continues until you have spent all your stored furniture bonus.
So, let's look at it all together. The furniture your house has, provides you with +10xp & let's say +35tp per hour. You log out in your house for 8 hours... you now have a rested +80xp & +280tp. Now, you go out and kill some mobs that are normally worth 100xp/10tp apiece. On your first kill you will receive 150xp & 15tp. This will leave you with +30xp & +275tp rested furniture bonus. On your second kill, you will receive 130xp & 15tp. This is because you only had +30 bonus xp remaining, and now it is spent. You now have +0xp & +270tp furniture bonus. So, on your third kill, you will receive +100xp & 15tp, which is what you will receive for your 4th & 5th.... and after 53 more kills, you will have finally spent your remaining bonus tp as well. Then the mobs will have returned to giving only 100xp/10tp per kill.
Bear in mind that furniture bonus xp/tp does not assist with quest turn-ins.