I have been having a problem trying to rid of the aphids that have infected a few of my indoor plants. At first sign, I tried a soap and water cleanse, but they came back. I tried neem oil, which didn't seem to do anything for the issue. More recently, I've used 'Garden Safe Brand Insecticidal Soap' which is killing them, but they keep returning and I'm unsure why.
In this type of situation, what do you recommend the best thing to use/do is? I keep feeling defeated that these pesky bugs won't die off. I don't want to lose these plants, as I've had them for over 20 years.