how long do love spells last?
it depends really. everyone has free will [the ability to think of yourself] a love spell cast over another is overpowering them and having them bend to your will. they will be subconciously fighting back to get control of their own desires once again, so it comes down to have strong willed the person is.
is there a way you can put a length on it?
not to my knowledge. if you cast a spell over another and then after a month or so get sick of them, you can cast another spell to undo the first one, or do a cleansing, but constantly casting and reversing isn't a good idea and the universe will punish you for not thinking things through.
is there a powerful love spell that does not require anything?
the power all spells draw from is found in nature. the items used in spellcasting add to the spells strength because they have similar properties for what you're casting for, in this case love. you could try a chant, if you pick the right time and charge a lot of energy, it can be powerful and work, but it carries a great chance of not working because you're relying on your focus, the energy you charged, and your visualization only. for someone who is not experienced with spells this can be a major challenge and could leave you seriously drained if you don't cast correctly.
do love spells make the person act stupid or does it seem natural and normal like you didn't cast anything?
while i would find it hilarious to see someone swooning over the caster with little hearts in their eyes, no, it'll seem 100% natural. really fast though, they'll be almost instantly in love with you and want to spend as much time as possible with you. sounds fun, but trust me it can get on your nerves if you like your space. [i've never cast a love spell on another for myself, but my boyfriend is very clingy by nature, and i like my space]
while it's harder, try to find love without making someone feel the same. it won't feel right in the long run. as always, be careful what you wish for, and think before you cast.