You're right, David, although "corre como si la vida depende de ello" sounds weird. In that case it's rather "dependiera".
Si + present is used when "si" introduces a condition, not a comparison.
Si vienes a visitarme, tomamos café.
If you come to visit me, we'll drink some coffee.
Si te gusta el futbol, vamos al estadio mañana.
If you like football, let's go to the stadium tomorrow.
Si no quiero hablar con nadie, me encierro en casa.
When/if I don't want to talk to anyone, I lock myself at home.
@Bob: "Gracias
por corregirlos"