The reason why I never really felt "at home" on this forum is likely that for all the complaining that's going on hardly anyone tries to understand her. I have read the most ridiculous stuff on here. Like when Together When.. released and someone said "It's about Tomoya" and someone else said "She's long over him!" Right.
She's all about searching for true love.
And she also knows that if you truely loved someone, you'll love that person forever. She knew that since her first album at the earliest, second album at the latest. I'd say Days is about the person she dated even before Nagase, so that you understand the scope, so to say. 11 years since breaking up is nothing for her. lol
I agree, though, that the lyrics can either be read to be about love or friendship. The friend of the past seems to be a common theme in her lyrics (see fairyland).
And saying Japanese people don't say "aishiteru" is like saying every Japanese eats sushi, or every Amrican watches football - you can't just generalise. How people use words is up to each individual, especially words of affection. Some might use "aishiteru" lightly, without any emotion behind it, some even sarcastically. How words are used also changes over time.